atan2
Returns the arctangent of Y/X in the range -pi to pi.
Returns the arctangent of Y/X in radians, using the signs of both
arguments to determine the quadrant. Both arguments are coerced to
Nv (f64). Stack order: Y is below X (Y pushed first).
Synopsis
my $angle = atan2(1, 1); # pi/4
my $pi = atan2(0, -1); # pi
my $angle = atan2($y, $x);