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cos |
Portability: | ISO/ANSI C conforming, UNIX compatible |
SYNOPSIS | |
DESCRIPTION | |
RETURN VALUE | |
DIAGNOSTICS | |
EXAMPLE | |
RELATED FUNCTIONS | |
SEE ALSO |
SYNOPSIS |
#include <math.h> double cos(double x);
DESCRIPTION |
cos
computes the trigonometric cosine of the value
x
. The
cos
function expects a value
of
x
expressed in radians.
Because the cosine function is periodic, only the value
of x mod 2 is used to compute the cosine. If
x
is very large, only a limited precision is left to represent x mod
2 . Thus, an error message is written for very large negative or positive
arguments (see DIAGNOSTICS below).
RETURN VALUE |
cos
returns the value of the cosine of the argument
x
, provided that this value is defined and computable. The return
value is of type
double
.
DIAGNOSTICS |
For a very large argument (
x
> 6.7465e9), the function returns 0.0. In this case, the message
"total loss of significance" is also written to
stderr
(the standard error file).
If an error occurs in
cos
, 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 cosine of a
60-degree angle using
cos
:
#include <stdio.h> #include <lcmath.h> main() { double y; /* The constant M_PI is declared in the */ /* header file . 60 degrees */ /* is pi/3 radians. */ y = cos(M_PI/3); printf("cos(%f) = %f\n",M_PI,y); }
RELATED FUNCTIONS |
SEE ALSO |
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