# Functions HI-TECH C ACOS

**ACOS, ASIN, ATAN, ATAN2**

## SYNOPSIS

#include <math.h> double acos(double f) double asin(double f) double atan(double f) double atan2(double x, double y)

## DESCRIPTION

These functions are the converse of the trignometric
functions cos, sin and tan. Acos and asin are undefined
for arguments whose absolute value is greater than 1.0.
The returned value is in radians, and always in the
range -pi/2 to +pi/2, except for **cos**(), which returns a
value in the range 0 to pi. **Atan2**() returns the
inverse tan of x/y but uses the signs of its arguments
to return a value in the range -pi to +pi.

## SEE ALSO

sin, cos, tan