osx man page for acos

ACOS(3) 						   BSD Library Functions Manual 						   ACOS(3)

NAME
     acos -- arc cosine function

SYNOPSIS
     #include <math.h>

     double
     acos(double x);

     long double
     acosl(long double x);

     float
     acosf(float x);

DESCRIPTION
     The acos() function computes the principle value of the arc cosine of x.  The result is in the range [0, pi].

SPECIAL VALUES
     acos(1) returns +0.

     acos(x) returns a NAN and raises the "invalid" floating-point exception for |x| > 1.

VECTOR OPERATIONS
     If you need to apply the acos() function to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may
     give significantly better performance:

     #include <Accelerate/Accelerate.h>

     vFloat vacosf(vFloat x);
     void vvacosf(float *y, const float *x, const int *n);
     void vvacos(double *y, const double *x, const int *n);

SEE ALSO
     sin(3), cos(3), tan(3), asin(3), atan(3), atan2(3), sinh(3), cosh(3), tanh(3), math(3)

STANDARDS
     The acos() function conforms to ISO/IEC 9899:2011.

BSD
								 December 11, 2006							       BSD