/C

# ccoshf, ccosh, ccoshl

Defined in header `<complex.h>`
`float complex       ccoshf( float complex z );`
(1) (since C99)
`double complex      ccosh( double complex z );`
(2) (since C99)
`long double complex ccoshl( long double complex z );`
(3) (since C99)
Defined in header `<tgmath.h>`
`#define cosh( z )`
(4) (since C99)
1-3) Computes the complex hyperbolic cosine of `z`.
4) Type-generic macro: If `z` has type `long double complex`, `ccoshl` is called. if `z` has type `double complex`, `ccosh` is called, if `z` has type `float complex`, `ccoshf` is called. If `z` is real or integer, then the macro invokes the corresponding real function (`coshf`, `cosh`, `coshl`). If `z` is imaginary, then the macro invokes the corresponding real version of the function `cos`, implementing the formula cosh(iy) = cos(y), and the return type is real.

### Parameters

 z - complex argument

### Return value

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

### Error handling and special values

Errors are reported consistent with math_errhandling.

If the implementation supports IEEE floating-point arithmetic,

• `ccosh(conj(z)) == conj(ccosh(z))`
• `ccosh(z) == ccosh(-z)`
• If `z` is `+0+0i`, the result is `1+0i`
• If `z` is `+0+∞i`, the result is `NaN±0i` (the sign of the imaginary part is unspecified) and `FE_INVALID` is raised
• If `z` is `+0+NaNi`, the result is `NaN±0i` (the sign of the imaginary part is unspecified)
• If `z` is `x+∞i` (for any finite non-zero x), the result is `NaN+NaNi` and `FE_INVALID` is raised
• If `z` is `x+NaNi` (for any finite non-zero x), the result is `NaN+NaNi` and `FE_INVALID` may be raised
• If `z` is `+∞+0i`, the result is `+∞+0i`
• If `z` is `+∞+yi` (for any finite non-zero y), the result is `+∞cis(y)`
• If `z` is `+∞+∞i`, the result is `±∞+NaNi` (the sign of the real part is unspecified) and `FE_INVALID` is raised
• If `z` is `+∞+NaN`, the result is `+∞+NaN`
• If `z` is `NaN+0i`, the result is `NaN±0i` (the sign of the imaginary part is unspecified)
• If `z` is `NaN+yi` (for any finite non-zero y), the result is `NaN+NaNi` and `FE_INVALID` may be raised
• If `z` is `NaN+NaNi`, the result is `NaN+NaNi`

where cis(y) is cos(y) + i sin(y).

Mathematical definition of hyperbolic cosine is cosh z =
 ez+e-z 2

Hyperbolic cosine is an entire function in the complex plane and has no branch cuts. It is periodic with respect to the imaginary component, with period 2πi.

### Example

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

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

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

Output:

```cosh(1+0i) = 1.543081+0.000000i (cosh(1)=1.543081)
cosh(0+1i) = 0.540302+0.000000i ( cos(1)=0.540302)```
• C11 standard (ISO/IEC 9899:2011):
• 7.3.6.4 The ccosh functions (p: 193)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• G.6.2.4 The ccosh functions (p: 541)
• G.7 Type-generic math <tgmath.h> (p: 545)
• C99 standard (ISO/IEC 9899:1999):
• 7.3.6.4 The ccosh functions (p: 175)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• G.6.2.4 The ccosh functions (p: 476)
• G.7 Type-generic math <tgmath.h> (p: 480)