# cacosf, cacos, cacosl

< c‎ | numeric‎ | complex

C
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Complex number arithmetic
Types and the imaginary constant
Manipulation
Power and exponential functions
Trigonometric functions
 cacos casin catan
Hyperbolic functions

 Defined in header `` float complex       cacosf( float complex z ); (1) (since C99) double complex      cacos( double complex z ); (2) (since C99) long double complex cacosl( long double complex z ); (3) (since C99) Defined in header `` #define acos( z ) (4) (since C99)
1-3) Computes the complex arc cosine of `z` with branch cuts outside the interval [−1,+1] along the real axis.
4) Type-generic macro: If `z` has type long double complex, `cacosl` is called. if `z` has type double complex, `cacos` is called, if `z` has type float complex, `cacosf` is called. If `z` is real or integer, then the macro invokes the corresponding real function (acosf, acos, acosl). If `z` is imaginary, then the macro invokes the corresponding complex number version.

## Contents

### Parameters

 z - complex argument

### Return value

If no errors occur, complex arc cosine of `z` is returned, in the range [0 ; ∞) along the real axis and in the range [−iπ ; iπ] along the imaginary axis.

### Error handling and special values

Errors are reported consistent with math_errhandling

If the implementation supports IEEE floating-point arithmetic,

• cacos(conj(z)) == conj(cacos(z))
• If `z` is `±0+0i`, the result is `π/2-0i`
• If `z` is `±0+NaNi`, the result is `π/2+NaNi`
• If `z` is `x+∞i` (for any finite x), the result is `π/2-∞i`
• If `z` is `x+NaNi` (for any nonzero finite x), the result is `NaN+NaNi` and FE_INVALID may be raised.
• If `z` is `-∞+yi` (for any positive finite y), the result is `π-∞i`
• If `z` is `-∞+yi` (for any positive finite y), the result is `+0-∞i`
• If `z` is `-∞+∞i`, the result is `3π/4-∞i`
• If `z` is `+∞+∞i`, the result is `π/4-∞i`
• If `z` is `±∞+NaNi`, the result is `NaN±∞i` (the sign of the imaginary part is unspecified)
• If `z` is `NaN+yi` (for any finite y), the result is `NaN+NaNi` and FE_INVALID may be raised
• If `z` is `NaN+∞i`, the result is `NaN-∞i`
• If `z` is `NaN+NaNi`, the result is `NaN+NaNi`