hv.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
 * are met:
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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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 */

/**
 * @file  hv.c
 * @brief Haversed sine function
 */

#include "prim.h"

/**
 * @brief   Haversed sine function
 * @details
 * <pre>
 * hv(x) = (1-cos(x))/2
 * </pre>
 */
double hv(double x)
{
    double a = cos(x);
    double b = 1.0 - a;
    double c = b / 2.0;
    return c;
}