# ccosf, ccos, ccosl

< c‎ | numeric‎ | complex

C
 Language Headers Type support Program utilities Variadic function support Error handling Dynamic memory management Date and time utilities Strings library Algorithms Numerics Input/output support Localization support Atomic operations (C11) Thread support (C11) Technical Specifications

Complex number arithmetic
Types and the imaginary constant
Manipulation
Power and exponential functions
Trigonometric functions
 ccos csin ctan
Hyperbolic functions

 Defined in header  float complex       ccosf( float complex z ); (1) (since C99) double complex      ccos( double complex z ); (2) (since C99) long double complex ccosl( long double complex z ); (3) (since C99) Defined in header  #define cos( z ) (4) (since C99)
1-3) Computes the complex cosine of z.
4) Type-generic macro: If z has type long double complex, ccosl is called. if z has type double complex, ccos is called, if z has type float complex, ccosf is called. If z is real or integer, then the macro invokes the corresponding real function (cosf, cos, cosl). If z is imaginary, then the macro invokes the corresponding real version of the function cosh, implementing the formula cos(iy) = cosh(y), and the return type is real.

## Contents

### Parameters

 z - complex argument

### Return value

If no errors occur, the complex cosine of z is returned.

Errors and special cases are handled as if the operation is implemented by ccosh(I*z).

### Notes

The cosine is an entire function on the complex plane, and has no branch cuts.

Mathematical definition of the cosine is cos z =
 eiz+e-iz 2

### Example

#include <stdio.h>
#include <math.h>
#include <complex.h>

int main(void)
{
double complex z = ccos(1);  // behaves like real cosine along the real line
printf("cos(1+0i) = %f%+fi ( cos(1)=%f)\n", creal(z), cimag(z), cos(1));

double complex z2 = ccos(I); // behaves like real cosh along the imaginary line
printf("cos(0+1i) = %f%+fi (cosh(1)=%f)\n", creal(z2), cimag(z2), cosh(1));
}

Output:

cos(1+0i) = 0.540302-0.000000i ( cos(1)=0.540302)
cos(0+1i) = 1.543081-0.000000i (cosh(1)=1.543081)

### References

• C11 standard (ISO/IEC 9899:2011):
• 7.3.5.4 The ccos functions (p: 191)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• G.7 Type-generic math <tgmath.h> (p: 545)
• C99 standard (ISO/IEC 9899:1999):
• 7.3.5.4 The ccos functions (p: 173)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• G.7 Type-generic math <tgmath.h> (p: 480)