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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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