atan[procedure] atan z
[procedure] atan y x
R5RS, R6RS: arctan. two argument version calculates (angle (make-rectangular x y)).
R6RS specifies these boundary cases:
(atan -inf.0) => -π/2
(atan +inf.0) => π/2
SRFI-94: two arguments version signals error if y or x is not real.
|