NAME
cos, cosf, cosl - cosine function
SYNOPSIS
#include <math.h>
double cos(double x);
float cosf(float x);
long double cosl(long double x);
DESCRIPTION
These functions shall compute the cosine of their argument x, measured
in radians.
An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID
| FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
occurred.
RETURN VALUE
Upon successful completion, these functions shall return the cosine of
x.
If x is NaN, a NaN shall be returned.
If x is ±0, the value 1.0 shall be returned.
If x is ±Inf, a domain error shall occur, and either a NaN (if
supported), or an implementation-defined value shall be returned.
ERRORS
These functions shall fail if:
Domain Error
The x argument is ±Inf.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [EDOM]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid
floating-point exception shall be raised.
The following sections are informative.
EXAMPLES
Taking the Cosine of a 45-Degree Angle
#include <math.h>
...
double radians = 45 * M_PI / 180;
double result;
...
result = cos(radians);
APPLICATION USAGE
These functions may lose accuracy when their argument is near an odd
multiple of pi/2 or is far from 0.
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but
at least one of them must be non-zero.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
acos() , feclearexcept() , fetestexcept() , isnan() , sin() , tan() ,
the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18,
Treatment of Error Conditions for Mathematical Functions, <math.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .