Name
acos
Synopsis
Calculates the inverse cosine of a number
#include <math.h> doubleacos
( doublex
); floatacosf
( floatx
); (C99) long doubleacosl
( long doublex
); (C99)
acos()
implements the
inverse cosine function, commonly called arc cosine. The argument
x
must be between −1 and 1, inclusive: −1
≤ x
≤ 1. If x
is outside the function’s domain—that is, greater than 1 or less
than −1—the function incurs a domain error.
The return value is given in radians, and is thus in the range
0 ≤ acos(
x
)
≤ π.
Example
/*
* Calculate the pitch of a roof given
* the sloping width from eaves to ridge and
* the horizontal width of the floor below it.
*/
#define PI 3.141593
#define DEG_PER_RAD (180.0/PI)
double floor_width = 30.0;
double roof_width = 34.6;
double roof_pitch =acos
( floor_width / roof_width ) * DEG_PER_RAD ;
printf( "The pitch of the roof is %2.0f degrees.\n", roof_pitch );
This code produces the following output:
The pitch of the roof is 30 degrees.
See Also
The arc cosine functions for complex numbers: cacos()
, cacosf()
, and cacosl()
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