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acos |
Portability: | ISO/ANSI C conforming, UNIX compatible |
SYNOPSIS | |
DESCRIPTION | |
RETURN VALUE | |
DIAGNOSTICS | |
EXAMPLE | |
RELATED FUNCTIONS | |
SEE ALSO |
SYNOPSIS |
#include <math.h> double acos(double x);
DESCRIPTION |
acos
computes the trigonometric arc cosine of the argument
x
. The arc cosine function is the inverse of the trigonometric cosine
function and is expressed by the following relation:
x
is in the closed
interval [-1.0,1.0] .
RETURN VALUE |
acos
returns the principal value of the arc cosine of the argument
x
, provided that this value is defined and computable. The return
value is a double precision floating-point number in the closed interval [0,]
radians.
DIAGNOSTICS |
An error message is written to the standard
error file (
stderr
) by the run-time library
if
x
is not in the domain [-1.0,1.0]
. In this case, the function returns 0.0.
If an error occurs in
acos
, the
_matherr
routine is called.
You can supply your own version of
_matherr
to suppress the diagnostic message or modify the value returned.
EXAMPLE |
This example computes the value of pi:
#include <math.h> #include <stdio.h> main() { double pi; /* pi is equal to the arc cosine of .5 times 3. */ pi = 3 * acos(.5); printf("3 * acos(%f) = %f\n", .5, pi); }
RELATED FUNCTIONS |
SEE ALSO |
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