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LETTERacosULETTER The Arccosine function.

Overview
#include <math.h>

r = acos(x);

double r; // result
double x; // angle

Portability
ANSI

Description
The Arccosine routine is the opposite to the cosinus (x = acos(cos(x))). Because the cosinus is a periodic function it is constrained as [0,PI].

Note
Of course all trigonometric functions require the angle be expressed in radians. Pass the angle "w" expressed in degrees to
x = PI/180 * w
to receive its equivalent in radians in "x".

See also
cos , asin