Inverse trig functions and atan2

packages/math/readme.md

@@ -18,6 +18,22 @@ Gets the cos of input.
 
 Gets the tan of input.
 
+### fun -double !asin -double &input
+
+Finds the angle *x* in the range [-pi/2, pi/2] such that sin(x) equals the input.
+
+### fun -double !acos -double &input
+
+Finds the angle *x* in the range [0, pi] such that cos(x) equals the input.
+
+### fun -double !atan -double &input
+
+Finds the angle *x* in the range [-pi/2, pi/2] such that tan(x) equals the input.
+
+### fun -double !atan2 -double &y -double &x
+
+Finds the angle in the range (-pi, pi] between the positive x axis and the point (x,y). This is equivalent to atan(y/x) for positive values of x.
+
 ### fun -double !intexp -double &base -int &power
 
 Returns base^power, for positive integer values of power. Returns 1 if power is non-positive (and thus is inaccurate for negative values of power).