Add to/from radian helpers

maths.hpp

@@ -69,6 +69,19 @@ almost_equal (const Ta &a, const Tb &b) {
 }
 
 
+const double PI = 3.141592653589793238462643;
+
+inline double
+to_degreees (double radians) {
+    return radians * 180 / PI;
+}
+
+inline double
+to_radians (double degrees) {
+    return degrees / 180 * PI;
+}
+
+
 template <>
 bool
 almost_equal (const float &a, const float &b);