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<!-- %MENU% Math functions, useful constants, random numbers -->
<h2 class="chapter">19 Mathematics</h2>

<p>This chapter contains information about functions for performing
mathematical computations, such as trigonometric functions.  Most of
these functions have prototypes declared in the header file
<samp><span class="file">math.h</span></samp>.  The complex-valued functions are defined in
<samp><span class="file">complex.h</span></samp>. 
<a name="index-math_002eh-2066"></a><a name="index-complex_002eh-2067"></a>
All mathematical functions which take a floating-point argument
have three variants, one each for <code>double</code>, <code>float</code>, and
<code>long double</code> arguments.  The <code>double</code> versions are mostly
defined in ISO&nbsp;C89<!-- /@w -->.  The <code>float</code> and <code>long double</code>
versions are from the numeric extensions to C included in ISO&nbsp;C99<!-- /@w -->.

   <p>Which of the three versions of a function should be used depends on the
situation.  For most calculations, the <code>float</code> functions are the
fastest.  On the other hand, the <code>long double</code> functions have the
highest precision.  <code>double</code> is somewhere in between.  It is
usually wise to pick the narrowest type that can accommodate your data. 
Not all machines have a distinct <code>long double</code> type; it may be the
same as <code>double</code>.

<ul class="menu">
<li><a accesskey="1" href="Mathematical-Constants.html#Mathematical-Constants">Mathematical Constants</a>:       Precise numeric values for often-used
                                 constants. 
<li><a accesskey="2" href="Trig-Functions.html#Trig-Functions">Trig Functions</a>:               Sine, cosine, tangent, and friends. 
<li><a accesskey="3" href="Inverse-Trig-Functions.html#Inverse-Trig-Functions">Inverse Trig Functions</a>:       Arcsine, arccosine, etc. 
<li><a accesskey="4" href="Exponents-and-Logarithms.html#Exponents-and-Logarithms">Exponents and Logarithms</a>:     Also pow and sqrt. 
<li><a accesskey="5" href="Hyperbolic-Functions.html#Hyperbolic-Functions">Hyperbolic Functions</a>:         sinh, cosh, tanh, etc. 
<li><a accesskey="6" href="Special-Functions.html#Special-Functions">Special Functions</a>:            Bessel, gamma, erf. 
<li><a accesskey="7" href="Errors-in-Math-Functions.html#Errors-in-Math-Functions">Errors in Math Functions</a>:     Known Maximum Errors in Math Functions. 
<li><a accesskey="8" href="Pseudo_002dRandom-Numbers.html#Pseudo_002dRandom-Numbers">Pseudo-Random Numbers</a>:        Functions for generating pseudo-random
				 numbers. 
<li><a accesskey="9" href="FP-Function-Optimizations.html#FP-Function-Optimizations">FP Function Optimizations</a>:    Fast code or small code. 
</ul>

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