3 sin, cos, tan, asin, acos, atan, atan2 \- trigonometric functions
28 double atan2(double y, double x)
33 return trigonometric functions of radian arguments.
34 The magnitude of the argument should be checked
35 by the caller to make sure the result is meaningful.
38 returns the arc sine in the range
42 returns the arc cosine in the range
46 returns the arc tangent in the range
50 returns the arc tangent of
61 for arguments greater than about