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## Trigonometric Functions

These are the familiar `sin`, `cos`, and `tan` functions. The arguments to all of these functions are in units of radians; recall that pi radians equals 180 degrees.

The math library doesn't define a symbolic constant for pi, but you can define your own if you need one:

```#define PI 3.14159265358979323846264338327
```

You can also compute the value of pi with the expression ```acos (-1.0)```.

Function: double sin (double x)

This function returns the sine of x, where x is given in radians. The return value is in the range `-1` to `1`.

Function: double cos (double x)

This function returns the cosine of x, where x is given in radians. The return value is in the range `-1` to `1`.

Function: double tan (double x)

This function returns the tangent of x, where x is given in radians.

The following `errno` error conditions are defined for this function:

`ERANGE`
Mathematically, the tangent function has singularities at odd multiples of pi/2. If the argument x is too close to one of these singularities, `tan` sets `errno` to `ERANGE` and returns either positive or negative `HUGE_VAL`.

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