cospi, cospif, cospil, cospid32, cospid64, cospid128
From cppreference.com
| Defined in header <math.h>
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| float cospif( float arg ); |
(1) | (since C23) |
| double cospi( double arg ); |
(2) | (since C23) |
| long double cospil( long double arg ); |
(3) | (since C23) |
| _Decimal32 cospid32( _Decimal32 arg ); |
(4) | (since C23) |
| _Decimal64 cospid64( _Decimal64 arg ); |
(5) | (since C23) |
| _Decimal128 cospid128( _Decimal128 arg ); |
(6) | (since C23) |
| Defined in header <tgmath.h>
|
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| #define cospi( arg ) |
(7) | (since C23) |
1-6) Computes the cosine of
π·arg measured in radians, thus regarding arg as a measurement in half-revolutions.7) Type-generic macro: calls the correct function based on the type of arg. If the argument has integer type, (2) (
cospi) is called.|
The functions (4-6) are declared if and only if the implementation predefines |
(since C23) |
Parameters
| arg | - | floating-point value whose product with π represents an angle in radians
|
Return value
If no errors occur, the cosine of π·arg (cos(π×arg)) in the range [-1, +1], 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.
Example
Run this code
#include <errno.h> #include <fenv.h> #include <math.h> #include <stdio.h> #ifndef __GNUC__ #pragma STDC FENV_ACCESS ON #endif #if __STDC_VERSION__ < 202311L // A naive implementation of a subset of cospi family double cospi(double arg) { return cos(arg * (double)3.1415926535897932384626433); } #endif int main(void) { const double pi = acos(-1); // typical usage printf("cospi(1) = %f, cos(pi) = %f\n", cospi(1), cos(pi)); printf("cospi(0.5) = %f, cos(pi/2) = %f\n", cospi(0.5), cos(pi / 2)); printf("cospi(-0.75) = %f, cos(-3*pi/4) = %f\n", cospi(-0.75), cos(-3 * pi / 4)); // special values printf("cospi(+0) = %f\n", cospi(0.0)); printf("cospi(-0) = %f\n", cospi(-0.0)); // error handling feclearexcept(FE_ALL_EXCEPT); printf("cospi(INFINITY) = %f\n", cospi(INFINITY)); if (fetestexcept(FE_INVALID)) puts(" FE_INVALID raised"); }
Possible output:
cospi(1) = -1.000000, cos(pi) = -1.000000
cospi(0.5) = 0.000000, cos(pi/2) = 0.000000
cospi(-0.75) = -0.707107, cos(-3*pi/4) = -0.707107
cospi(+0) = 1.000000
cospi(-0) = 1.000000
cospi(INFINITY) = -nan
FE_INVALID raisedReferences
- C23 standard (ISO/IEC 9899:2024):
- 7.12.4.12 The cospi functions (p: 247)
- 7.27 Type generic math <tgmath.h> (p: 387)
See also
| (C99)(C99) |
computes cosine (cos(x)) (function) |