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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 .