cos, cosf, cosl
Defined in header <math.h>
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(1) | (since C99) |
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(2) | |
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(3) | (since C99) |
Defined in header <tgmath.h>
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(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
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 arg is large.
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(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
#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:
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 (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 (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) |
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