COS(P) POSIX Programmer's Manual COS(P)
cos, cosf, cosl - cosine function
double cos(double x);
float cosf(float x);
long double cosl(long double x);
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.
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 imple-
mentation-defined value shall be returned.
These functions shall fail if:
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.
Taking the Cosine of a 45-Degree Angle
double radians = 45 * M_PI / 180;
result = cos(radians);
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.
acos() , feclearexcept() , fetestexcept() , isnan() , sin() , tan() , the Base Definitions
volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathemati-
cal Functions, <math.h>
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 COS(P)