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# Tangent

> Evaluate the [tangent][tangent] of a number.

<section class="intro">

The [tangent][tangent] is defined as

<!-- <equation class="equation" label="eq:tangent" align="center" raw="\tan x = \frac{\sin x}{\cos x}" alt="Tangent definition."> -->

<div class="equation" align="center" data-raw-text="\tan x = \frac{\sin x}{\cos x}" data-equation="eq:tangent">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/tan/docs/img/equation_tangent.svg" alt="Tangent definition.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var tan = require( '@stdlib/math/base/special/tan' );
```

#### tan( x )

Evaluates the [tangent][tangent] of a `number` (in radians).

```javascript
var v = tan( 0.0 );
// returns ~0.0

v = tan( -3.141592653589793/4.0 );
// returns ~-1.0

v = tan( 3.141592653589793/4.0 );
// returns ~1.0

v = tan( NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var linspace = require( '@stdlib/array/linspace' );
var PI = require( '@stdlib/constants/float64/pi' );
var tan = require( '@stdlib/math/base/special/tan' );

var x = linspace( -PI/2.0, PI/2.0, 100 );
var i;

for ( i = 0; i < x.length; i++ ) {
    console.log( tan( x[ i ] ) );
}
```

</section>

<!-- /.examples -->

<section class="links">

[tangent]: http://mathworld.wolfram.com/Tangent.html

</section>

<!-- /.links -->