# libm.info: acos

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# `acos', `acosf'--arc cosine

*Synopsis*
#include <math.h>
double acos(double X);
float acosf(float X);
*Description*
`acos' computes the inverse cosine (arc cosine) of the input value.
Arguments to `acos' must be in the range -1 to 1.

`acosf' is identical to `acos', except that it performs its
calculations on `floats'.

*Returns*
`acos' and `acosf' return values in radians, in the range of 0 to pi.

If X is not between -1 and 1, the returned value is NaN (not a number)
the global variable `errno' is set to `EDOM', and a `DOMAIN error'
message is sent as standard error output.

You can modify error handling for these functions using `matherr'.

Created Mon Nov 8 17:42:56 2004 on tillpc with info_to_html version 0.9.6.