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## 19 Mathematics

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 `math.h`. The complex-valued functions are defined in `complex.h`. All mathematical functions which take a floating-point argument have three variants, one each for `double`, `float`, and `long double` arguments. The `double` versions are mostly defined in ISO C89. The `float` and `long double` versions are from the numeric extensions to C included in ISO C99.

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