mirror of
https://github.com/BelfrySCAD/BOSL2.git
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394 lines
16 KiB
OpenSCAD
394 lines
16 KiB
OpenSCAD
//////////////////////////////////////////////////////////////////////
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// LibFile: trigonometry.scad
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// Trigonometry shortcuts for people who can't be bothered to remember
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// all the function relations, or silly acronyms like SOHCAHTOA.
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// Includes:
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// include <BOSL2/std.scad>
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// FileGroup: Math
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// FileSummary: Trigonometry shortcuts for when you can't recall the mnemonic SOHCAHTOA.
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// FileFootnotes: STD=Included in std.scad
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//////////////////////////////////////////////////////////////////////
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// Section: 2D General Triangle Functions
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// Function: law_of_cosines()
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// Usage:
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// C = law_of_cosines(a, b, c);
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// c = law_of_cosines(a, b, C=);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Applies the Law of Cosines for an arbitrary triangle. Given three side lengths, returns the
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// angle in degrees for the corner opposite of the third side. Given two side lengths, and the
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// angle between them, returns the length of the third side.
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// Figure(2D):
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// stroke([[-50,0], [10,60], [50,0]], closed=true);
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// color("black") {
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// translate([ 33,35]) text(text="a", size=8, halign="center", valign="center");
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// translate([ 0,-6]) text(text="b", size=8, halign="center", valign="center");
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// translate([-22,35]) text(text="c", size=8, halign="center", valign="center");
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// }
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// color("blue") {
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// translate([-37, 6]) text(text="A", size=8, halign="center", valign="center");
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// translate([ 9,51]) text(text="B", size=8, halign="center", valign="center");
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// translate([ 38, 6]) text(text="C", size=8, halign="center", valign="center");
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// }
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// Arguments:
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// a = The length of the first side.
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// b = The length of the second side.
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// c = The length of the third side.
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// ---
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// C = The angle in degrees of the corner opposite of the third side.
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// See Also: law_of_sines()
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function law_of_cosines(a, b, c, C) =
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// Triangle Law of Cosines:
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// c^2 = a^2 + b^2 - 2*a*b*cos(C)
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assert(num_defined([c,C]) == 1, "Must give exactly one of c= or C=.")
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is_undef(c) ? sqrt(a*a + b*b - 2*a*b*cos(C)) :
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acos(constrain((a*a + b*b - c*c) / (2*a*b), -1, 1));
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// Function: law_of_sines()
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// Usage:
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// B = law_of_sines(a, A, b);
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// b = law_of_sines(a, A, B=);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Applies the Law of Sines for an arbitrary triangle. Given two triangle side lengths and the
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// angle between them, returns the angle of the corner opposite of the second side. Given a side
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// length, the opposing angle, and a second angle, returns the length of the side opposite of the
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// second angle.
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// Figure(2D):
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// stroke([[-50,0], [10,60], [50,0]], closed=true);
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// color("black") {
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// translate([ 33,35]) text(text="a", size=8, halign="center", valign="center");
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// translate([ 0,-6]) text(text="b", size=8, halign="center", valign="center");
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// translate([-22,35]) text(text="c", size=8, halign="center", valign="center");
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// }
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// color("blue") {
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// translate([-37, 6]) text(text="A", size=8, halign="center", valign="center");
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// translate([ 9,51]) text(text="B", size=8, halign="center", valign="center");
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// translate([ 38, 6]) text(text="C", size=8, halign="center", valign="center");
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// }
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// Arguments:
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// a = The length of the first side.
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// A = The angle in degrees of the corner opposite of the first side.
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// b = The length of the second side.
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// ---
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// B = The angle in degrees of the corner opposite of the second side.
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// See Also: law_of_cosines()
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function law_of_sines(a, A, b, B) =
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// Triangle Law of Sines:
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// a/sin(A) = b/sin(B) = c/sin(C)
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assert(num_defined([b,B]) == 1, "Must give exactly one of b= or B=.")
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let( r = a/sin(A) )
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is_undef(b) ? r*sin(B) :
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asin(constrain(b/r, -1, 1));
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// Function: triangle_area()
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// Usage:
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// area = triangle_area(p1,p2,p3);
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// Topics: Geometry, Trigonometry, Triangles, Area
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// Description:
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// Returns the area of a triangle formed between three 2D or 3D vertices.
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// Result will be negative if the points are 2D and in clockwise order.
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// Arguments:
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// p1 = The first vertex of the triangle.
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// p2 = The second vertex of the triangle.
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// p3 = The third vertex of the triangle.
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// Example:
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// triangle_area([0,0], [5,10], [10,0]); // Returns -50
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// triangle_area([10,0], [5,10], [0,0]); // Returns 50
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function triangle_area(p1,p2,p3) =
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assert( is_path([p1,p2,p3]), "Invalid points or incompatible dimensions." )
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len(p1)==3
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? 0.5*norm(cross(p3-p1,p3-p2))
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: 0.5*cross(p3-p1,p3-p2);
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// Section: 2D Right Triangle Functions
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// This is a set of functions to make it easier to perform trig calculations on right triangles.
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// In general, all these functions are named using these abbreviations:
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// - **hyp**: The length of the Hypotenuse.
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// - **adj**: The length of the side adjacent to the angle.
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// - **opp**: The length of the side opposite to the angle.
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// - **ang**: The angle size in degrees.
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// .
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// If you know two of those, and want to know the value of a third, you will need to call a
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// function named like `AAA_BBB_to_CCC()`. For example, if you know the length of the hypotenuse,
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// and the length of the side adjacent to the angle, and want to learn the length of the side
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// opposite to the angle, you will call `opp = hyp_adj_to_opp(hyp,adj);`.
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// Figure(2D):
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// color("brown") {
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// stroke([[40,0], [40,10], [50,10]]);
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// left(50) stroke(arc(r=37,angle=30));
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// }
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// color("lightgreen") stroke([[-50,0], [50,60], [50,0]], closed=true);
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// color("black") {
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// translate([ 62,25]) text(text="opp", size=8, halign="center", valign="center");
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// translate([ 0,-6]) text(text="adj", size=8, halign="center", valign="center");
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// translate([ 0,40]) text(text="hyp", size=8, halign="center", valign="center");
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// translate([-25, 5]) text(text="ang", size=7, halign="center", valign="center");
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// }
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// Function: hyp_opp_to_adj()
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// Alias: opp_hyp_to_adj()
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// Usage:
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// adj = hyp_opp_to_adj(hyp,opp);
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// adj = opp_hyp_to_adj(opp,hyp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the lengths of the hypotenuse and opposite side of a right triangle, returns the length
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// of the adjacent side.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// Example:
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// hyp = hyp_opp_to_adj(5,3); // Returns: 4
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function hyp_opp_to_adj(hyp,opp) =
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assert(is_finite(hyp+opp) && hyp>=0 && opp>=0,
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"Triangle side lengths should be a positive numbers." )
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sqrt(hyp*hyp-opp*opp);
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function opp_hyp_to_adj(opp,hyp) = hyp_opp_to_adj(hyp,opp);
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// Function: hyp_ang_to_adj()
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// Alias: ang_hyp_to_adj()
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// Usage:
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// adj = hyp_ang_to_adj(hyp,ang);
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// adj = ang_hyp_to_adj(ang,hyp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the length of the hypotenuse and the angle of the primary corner of a right triangle,
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// returns the length of the adjacent side.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// adj = hyp_ang_to_adj(8,60); // Returns: 4
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function hyp_ang_to_adj(hyp,ang) =
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assert(is_finite(hyp) && hyp>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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hyp*cos(ang);
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function ang_hyp_to_adj(ang,hyp) = hyp_ang_to_adj(hyp, ang);
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// Function: opp_ang_to_adj()
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// Alias: ang_opp_to_adj()
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// Usage:
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// adj = opp_ang_to_adj(opp,ang);
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// adj = ang_opp_to_adj(ang,opp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the angle of the primary corner of a right triangle, and the length of the side opposite of it,
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// returns the length of the adjacent side.
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// Arguments:
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// adj = opp_ang_to_adj(8,30); // Returns: 4
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function opp_ang_to_adj(opp,ang) =
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assert(is_finite(opp) && opp>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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opp/tan(ang);
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function ang_opp_to_adj(ang,opp) = opp_ang_to_adj(opp,ang);
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// Function: hyp_adj_to_opp()
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// Alias: adj_hyp_to_opp()
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// Usage:
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// opp = hyp_adj_to_opp(hyp,adj);
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// opp = adj_hyp_to_opp(adj,hyp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the length of the hypotenuse and the adjacent side, returns the length of the opposite side.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// Example:
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// opp = hyp_adj_to_opp(5,4); // Returns: 3
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function hyp_adj_to_opp(hyp,adj) =
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assert(is_finite(hyp) && hyp>=0 && is_finite(adj) && adj>=0,
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"Triangle side lengths should be a positive numbers." )
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sqrt(hyp*hyp-adj*adj);
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function adj_hyp_to_opp(adj,hyp) = hyp_adj_to_opp(hyp,adj);
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// Function: hyp_ang_to_opp()
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// Alias: ang_hyp_to_opp()
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// Usage:
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// opp = hyp_ang_to_opp(hyp,ang);
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// opp = ang_hyp_to_opp(ang,hyp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the length of the hypotenuse of a right triangle, and the angle of the corner, returns the length of the opposite side.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// opp = hyp_ang_to_opp(8,30); // Returns: 4
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function hyp_ang_to_opp(hyp,ang) =
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assert(is_finite(hyp)&&hyp>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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hyp*sin(ang);
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function ang_hyp_to_opp(ang,hyp) = hyp_ang_to_opp(hyp,ang);
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// Function: adj_ang_to_opp()
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// Alias: ang_adj_to_opp()
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// Usage:
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// opp = adj_ang_to_opp(adj,ang);
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// opp = ang_adj_to_opp(ang,adj);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the length of the adjacent side of a right triangle, and the angle of the corner, returns the length of the opposite side.
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// Arguments:
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// opp = adj_ang_to_opp(8,45); // Returns: 8
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function adj_ang_to_opp(adj,ang) =
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assert(is_finite(adj)&&adj>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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adj*tan(ang);
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function ang_adj_to_opp(ang,adj) = adj_ang_to_opp(adj,ang);
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// Function: adj_opp_to_hyp()
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// Alias: opp_adj_to_hyp()
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// Usage:
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// hyp = adj_opp_to_hyp(adj,opp);
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// hyp = opp_adj_to_hyp(opp,adj);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// Given the length of the adjacent and opposite sides of a right triangle, returns the length of thee hypotenuse.
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// Arguments:
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// Example:
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// hyp = adj_opp_to_hyp(3,4); // Returns: 5
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function adj_opp_to_hyp(adj,opp) =
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assert(is_finite(opp) && opp>=0 && is_finite(adj) && adj>=0,
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"Triangle side lengths should be a positive numbers." )
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norm([opp,adj]);
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function opp_adj_to_hyp(opp,adj) = adj_opp_to_hyp(adj,opp);
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// Function: adj_ang_to_hyp()
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// Alias: ang_adj_to_hyp()
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// Usage:
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// hyp = adj_ang_to_hyp(adj,ang);
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// hyp = ang_adj_to_hyp(ang,adj);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// For a right triangle, given the length of the adjacent side, and the corner angle, returns the length of the hypotenuse.
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// Arguments:
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// hyp = adj_ang_to_hyp(4,60); // Returns: 8
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function adj_ang_to_hyp(adj,ang) =
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assert(is_finite(adj) && adj>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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adj/cos(ang);
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function ang_adj_to_hyp(ang,adj) = adj_ang_to_hyp(adj,ang);
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// Function: opp_ang_to_hyp()
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// Alias: ang_opp_to_hyp()
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// Usage:
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// hyp = opp_ang_to_hyp(opp,ang);
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// hyp = ang_opp_to_hyp(ang,opp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// For a right triangle, given the length of the opposite side, and the corner angle, returns the length of the hypotenuse.
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// Arguments:
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// ang = The angle in degrees of the primary corner of the right triangle.
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// Example:
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// hyp = opp_ang_to_hyp(4,30); // Returns: 8
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function opp_ang_to_hyp(opp,ang) =
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assert(is_finite(opp) && opp>=0, "Triangle side length should be a positive number." )
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assert(is_finite(ang) && ang>-90 && ang<90, "The angle should be an acute angle." )
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opp/sin(ang);
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function ang_opp_to_hyp(ang,opp) = opp_ang_to_hyp(opp,ang);
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// Function: hyp_adj_to_ang()
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// Alias: adj_hyp_to_ang()
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// Usage:
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// ang = hyp_adj_to_ang(hyp,adj);
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// ang = adj_hyp_to_ang(adj,hyp);
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// Description:
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// For a right triangle, given the lengths of the hypotenuse and the adjacent sides, returns the angle of the corner.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// Example:
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// ang = hyp_adj_to_ang(8,4); // Returns: 60 degrees
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function hyp_adj_to_ang(hyp,adj) =
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assert(is_finite(hyp) && hyp>0 && is_finite(adj) && adj>=0,
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"Triangle side lengths should be positive numbers." )
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acos(adj/hyp);
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function adj_hyp_to_ang(adj,hyp) = hyp_adj_to_ang(hyp,adj);
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// Function: hyp_opp_to_ang()
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// Alias: opp_hyp_to_ang()
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// Usage:
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// ang = hyp_opp_to_ang(hyp,opp);
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// ang = opp_hyp_to_ang(opp,hyp);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// For a right triangle, given the lengths of the hypotenuse and the opposite sides, returns the angle of the corner.
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// Arguments:
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// hyp = The length of the hypotenuse of the right triangle.
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// Example:
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// ang = hyp_opp_to_ang(8,4); // Returns: 30 degrees
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function hyp_opp_to_ang(hyp,opp) =
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assert(is_finite(hyp+opp) && hyp>0 && opp>=0,
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"Triangle side lengths should be positive numbers." )
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asin(opp/hyp);
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function opp_hyp_to_ang(opp,hyp) = hyp_opp_to_ang(hyp,opp);
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// Function: adj_opp_to_ang()
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// Alias: opp_adj_to_ang()
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// Usage:
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// ang = adj_opp_to_ang(adj,opp);
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// ang = opp_adj_to_ang(opp,adj);
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// Topics: Geometry, Trigonometry, Triangles
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// Description:
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// For a right triangle, given the lengths of the adjacent and opposite sides, returns the angle of the corner.
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// Arguments:
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// adj = The length of the side of the right triangle that is adjacent to the primary angle.
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// opp = The length of the side of the right triangle that is opposite from the primary angle.
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// Example:
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// ang = adj_opp_to_ang(sqrt(3)/2,0.5); // Returns: 30 degrees
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function adj_opp_to_ang(adj,opp) =
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assert(is_finite(adj+opp) && adj>0 && opp>=0,
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"Triangle side lengths should be positive numbers." )
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atan2(opp,adj);
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function opp_adj_to_ang(opp,adj) = adj_opp_to_ang(adj,opp);
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// vim: expandtab tabstop=4 shiftwidth=4 softtabstop=4 nowrap
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