Trigonometry is an important part of mathematics and PHP’s math functions provides us with some functions which are very useful for calculations involving trigonometry.The *tan()* function in PHP is used to find the tangent of the argument parameter.

The argument parameter must be in radians.

**Syntax:**

floattan($value)

**Parameters:** This function accepts a single parameter *$value*. It is the number whose tangent value you want to find. The value of this parameter must be in radians.

**Return Value:** It returns a floating point number which is the tangent value of number passed to it as argument.

Examples:

Input : tan(0.50) Output : 0.54630248984379 Input : tan(-0.50) Output : -0.54630248984379 Input : tan(5) Output : -3.3805150062466 Input : tan(M_PI_4) Output : 1

Below programs illustrate tan() in PHP:

- Passing 0.50 as a parameter:
`<?php`

`echo`

`(tan(0.50));`

`?>`

Output:

0.54630248984379

- Passing -0.50 as a parameter:
`<?php`

`echo`

`(tan(-0.50));`

`?>`

Output:

-0.54630248984379

- Passing 5 as a parameter:
`<?`

`php`

`echo (tan(5));`

`?>`

Output:

-3.3805150062466

- When (M_PI_4) is passed as a parameter, M_PI_4 is a constant in PHP whose value is 0.78539816339744830962:
`<?php`

`echo`

`(tan(M_PI_4));`

`?>`

Output:

1

**Reference**:

http://php.net/manual/en/function.tan.php

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