The mathLib.atan2() system function computes the principal value of the arc tangent of y/x, using the signs of both arguments to determine the quadrant of the return value.
mathLib.atan2(
y FLOAT in,
x FLOAT in)
returns (result FLOAT)
x INT = 5;
y INT = 1;
result FLOAT = mathLib.atan2(y, x);
// result is 0.19739555984988078