cacosh.c

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/*-
 * Copyright (c) 2014-2018 Carsten Sonne Larsen <cs@innolan.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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#include "prim.h"

/**
 * @brief  Inverse hyperbolic cosine of complex number
 * @details
 * Inverse hyperbolic cosine expressed using complex logarithms:
 * <pre>
 * acosh(z) = log(z + sqrt(z*z - 1))
 * </pre>
 * More info is available at Wikipedia: <BR>
 * https://wikipedia.org/wiki/Inverse_hyperbolic_function#Logarithmic_representation
 */
complex cacosh(complex z)
{
    complex one = cpack(1.0, 0.0);
    complex a = csub(cmul(z, z), one);
    complex b = cadd(z, csqrt(a));
    complex w = clog(b);
    return w;
}