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| <h3 class="section">1.4 <code>acosh</code>, <code>acoshf</code>—inverse hyperbolic cosine</h3> |
| |
| <p><a name="index-acosh-7"></a><a name="index-acoshf-8"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| double acosh(double <var>x</var>); |
| float acoshf(float <var>x</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| <code>acosh</code> calculates the inverse hyperbolic cosine of <var>x</var>. |
| <code>acosh</code> is defined as |
| <pre class="smallexample"> log(<var>x</var> + sqrt(<var>x</var>*<var>x</var>-1)) |
| </pre> |
| <p><var>x</var> must be a number greater than or equal to 1. |
| |
| <p><code>acoshf</code> is identical, other than taking and returning floats. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>acosh</code> and <code>acoshf</code> return the calculated value. If <var>x</var> |
| less than 1, the return value is NaN and <code>errno</code> is set to <code>EDOM</code>. |
| |
| <p>You can change the error-handling behavior with the non-ANSI |
| <code>matherr</code> function. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| Neither <code>acosh</code> nor <code>acoshf</code> are ANSI C. They are not recommended |
| for portable programs. |
| |
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