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Math Library (libm, -lm)

#include <complex.h>

The
`csqrt()`,
`csqrtf()`,
and
`csqrtl()`
functions compute the square root of
z
in the complex plane, with a branch cut along the negative real axis.
In other words,
`csqrt()`,
`csqrtf()`,
and
`csqrtl()`
always return the square root whose real part is non-negative.

These functions return the requested square root.
The square root of 0 is
`+0 ± 0`,
where the imaginary parts of the input and respective result have
the same sign.
For infinities and NaNs, the following rules apply, with the
earlier rules having precedence:
* Input*

*
*

Result | ||

k + ∞*I | ∞ + ∞*I | (for all k) |

-∞ + NaN*I | NaN ± ∞*I | |

∞ + NaN*I | ∞ + NaN*I | |

k + NaN*I | NaN + NaN*I | |

NaN + k*I | NaN + NaN*I | |

-∞ + k*I | +0 + ∞*I | |

∞ + k*I | ∞ + 0*I |

For numbers with negative imaginary parts, the above special cases apply given the identity:

` csqrt(conj(z) = conj(sqrt(z))`

Note that the sign of NaN is indeterminate. Also, if the real or imaginary part of the input is finite and an NaN is generated, an invalid exception will be thrown.

The
`csqrt()`,
`csqrtf()`,
and
`csqrtl()`
functions conform to
ISO/IEC 9899:1999 ("ISO C99").

For
`csqrt()`
and
`csqrtl()`,
inexact results are not always correctly rounded.

CSQRT (3) | March 30, 2008 |

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