Added degrees, radians and rot2_z() to maths.scad.

readme.md

@@ -5283,17 +5283,21 @@ Maths utilities for manipulating vectors and matrices.
 |:--- |:--- |
 | ```angle_between(v1, v2)``` | Return the angle between two vectors |
 | ```augment(m)``` | Augment a matrix by adding an identity matrix to the right |
+| ```degrees(radians)``` | Convert degrees to radians |
 | ```euler(R)``` | Convert a rotation matrix to a Euler rotation vector. |
 | ```identity(n, x = 1)``` | Construct an arbitrary size identity matrix |
 | ```invert(m)``` | Invert a matrix |
 | ```nearly_zero(x)``` | True if x is close to zero |
+| ```radians(degrees)``` | Convert radians to degrees |
 | ```reverse(v)``` | Reverse a vector |
+| ```rot2_z(a)``` | Generate a 2x2 matrix to rotate around z |
 | ```rot3_z(a)``` | Generate a 3x3 matrix to rotate around z |
 | ```rotate(a, v)``` | Generate a 4x4 rotation matrix, ```a``` can be a vector of three angles or a single angle around ```z```, or around axis ```v``` |
 | ```rowswap(m, i, j)``` | Swap two rows of a matrix |
 | ```scale(v)``` |  Generate a 4x4 matrix that scales by ```v```, which can be a vector of xyz factors or a scalar to scale all axes equally |
 | ```solve(m, i = 0, j = 0)``` | Solve each row ensuring diagonal is not zero |
 | ```solve_row(m, i)``` | Make diagonal one by dividing the row by it and subtract from other rows to make column zero |
+| ```sqr(x)``` | Square x |
 | ```transform(v, m)``` | Apply 4x4 transform to a 3 vector by extending it and cropping it again |
 | ```transform_points(path, m)``` | Apply transform to a path |
 | ```translate(v)``` | Generate a 4x4 translation matrix, ```v``` can be ```[x, y]```, ```[x, y, z]``` or ```z``` |

utils/maths.scad

@@ -20,7 +20,10 @@
 //
 //! Maths utilities for manipulating vectors and matrices.
 //
-function sqr(x) = x * x;
+function sqr(x) = x * x;                        //! Square x
+function radians(degrees) = degrees * PI / 180; //! Convert radians to degrees
+function degrees(radians) = radians * 180 / PI; //! Convert degrees to radians
+
 
 function translate(v) = let(u = is_list(v) ? len(v) == 2 ? [v.x, v.y, 0] //! Generate a 4x4 translation matrix, ```v``` can be ```[x, y]```, ```[x, y, z]``` or ```z```
                                                          : v
@@ -63,6 +66,12 @@ function rot3_z(a) = //! Generate a 3x3 matrix to rotate around z
           [ s,  c,  0],
           [ 0,  0,  1] ];
 
+function rot2_z(a) = //! Generate a 2x2 matrix to rotate around z
+    let(c = cos(a),
+        s = sin(a))
+        [ [ c, -s],
+          [ s,  c] ];
+
 function scale(v) = let(s = is_list(v) ? v : [v, v, v]) //!  Generate a 4x4 matrix that scales by ```v```, which can be a vector of xyz factors or a scalar to scale all axes equally
                         [
                           [s.x, 0,   0,   0],