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| <h3 class="section">1.3 <code>acos</code>, <code>acosf</code>—arc cosine</h3> |
| |
| <p><a name="index-acos-5"></a><a name="index-acosf-6"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| double acos(double <var>x</var>); |
| float acosf(float <var>x</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| |
| <p><code>acos</code> computes the inverse cosine (arc cosine) of the input value. |
| Arguments to <code>acos</code> must be in the range −1 to 1. |
| |
| <p><code>acosf</code> is identical to <code>acos</code>, except that it performs |
| its calculations on <code>floats</code>. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>acos</code> and <code>acosf</code> return values in radians, in the range of 0 to pi. |
| |
| <p>If <var>x</var> is not between −1 and 1, the returned value is NaN |
| (not a number) the global variable <code>errno</code> is set to <code>EDOM</code>, and a |
| <code>DOMAIN error</code> message is sent as standard error output. |
| |
| <p>You can modify error handling for these functions using <code>matherr</code>. |
| |
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