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| <h3 class="section">1.17 <code>expm1</code>, <code>expm1f</code>—exponential minus 1</h3> |
| |
| <p><a name="index-expm1-43"></a><a name="index-expm1f-44"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| double expm1(double <var>x</var>); |
| float expm1f(float <var>x</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| <code>expm1</code> and <code>expm1f</code> calculate the exponential of <var>x</var> |
| and subtract 1, that is, |
| e raised to the power <var>x</var> minus 1 (where e |
| is the base of the natural system of logarithms, approximately |
| 2.71828). The result is accurate even for small values of |
| <var>x</var>, where using <code>exp(</code><var>x</var><code>)-1</code> would lose many |
| significant digits. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| e raised to the power <var>x</var>, minus 1. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| Neither <code>expm1</code> nor <code>expm1f</code> is required by ANSI C or by |
| the System V Interface Definition (Issue 2). |
| |
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