Defined in header <math.h> | ||||
---|---|---|---|---|
| (1) | (since C99) | ||
| (2) | |||
| (3) | (since C99) | ||
Defined in header <tgmath.h> | ||||
| (4) | (since C99) |
1-3) Computes the cosine of
arg
(measured in radians). 4) Type-generic macro: If the argument has type
long double
, cosl
is called. Otherwise, if the argument has integer type or the type double
, cos
is called. Otherwise, cosf
is called. If the argument is complex, then the macro invokes the corresponding complex function (ccosf
, ccos
, ccosl
).Parameters
arg | - | floating point value representing angle in radians |
Return value
Return value
If no errors occur, the cosine of arg
(cos(arg)) in the range [-1 ; +1], is returned.
The result may have little or no significance if the magnitude of | (until C++11) |
If a domain error occurs, an implementation-defined value is returned (NaN where supported).
If a range error occurs due to underflow, the correct result (after rounding) is returned.
Error handling
Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- if the argument is ±0, the result is 1.0
- if the argument is ±∞, NaN is returned and
FE_INVALID
is raised - if the argument is NaN, NaN is returned
Notes
The case where the argument is infinite is not specified to be a domain error in C, but it is defined as a domain error in POSIX.
Example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | #include <stdio.h> #include <math.h> #include <errno.h> #include <fenv.h> #pragma STDC FENV_ACCESS ON int main( void ) { double pi = acos (-1); // typical usage printf ( "cos(pi/3) = %f\n" , cos (pi/3)); printf ( "cos(pi/2) = %f\n" , cos (pi/2)); printf ( "cos(-3*pi/4) = %f\n" , cos (-3*pi/4)); // special values printf ( "cos(+0) = %f\n" , cos (0.0)); printf ( "cos(-0) = %f\n" , cos (-0.0)); // error handling feclearexcept(FE_ALL_EXCEPT); printf ( "cos(INFINITY) = %f\n" , cos (INFINITY)); if (fetestexcept(FE_INVALID)) puts ( " FE_INVALID raised" ); } |
Possible output:
1 2 3 4 5 6 7 | cos (pi/3) = 0.500000 cos (pi/2) = 0.000000 cos (-3*pi/4) = -0.707107 cos (+0) = 1.000000 cos (-0) = 1.000000 cos (INFINITY) = -nan FE_INVALID raised |
References
- C11 standard (ISO/IEC 9899:2011):
- 7.12.4.5 The cos functions (p: 239)
- 7.25 Type-generic math <tgmath.h> (p: 373-375)
- F.10.1.5 The cos functions (p: 519)
- C99 standard (ISO/IEC 9899:1999):
- 7.12.4.5 The cos functions (p: 220)
- 7.22 Type-generic math <tgmath.h> (p: 335-337)
- F.9.1.5 The cos functions (p: 456)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.5.2.5 The cos function
See also
(C99)(C99) | computes sine (sin(x)) (function) |
(C99)(C99) | computes tangent (tan(x)) (function) |
(C99)(C99) | computes arc cosine (arccos(x)) (function) |
(C99)(C99)(C99) | computes the complex cosine (function) |
C++ documentation for cos |
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