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 *cos()*function in PHP is used to find the cosine of a number.

The cos() function returns a float value between -1 and 1, which represents the cosine of the angle. The argument passed to it must be in radians.

**Syntax:**

floatcos($value)

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

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

Examples:

Input : cos(3) Output : -0.98999249660045 Input : cos(-3) Output : -0.98999249660045 Input : cos(2*M_PI) Output : 1 Input : cos(0) Output : 1

Below programs illustrate cos() function in PHP:

- Passing 3 as a parameter:
`<?`

`php`

`echo (cos(3));`

`?>`

Output:

-0.98999249660045

- Passing -3 as a parameter:
`<?`

`php`

`echo (cos(-3));`

`?>`

Output:

-0.98999249660045

- When (2*M_PI) is passed as a parameter, M_PI is a constant in PHP whose value is 3.1415926535898:
`<?`

`php`

`echo (cos(2*M_PI));`

`?>`

Output:

1

- Passing 0 as a parameter:
`<?`

`php`

`echo (cos(0));`

`?>`

Output:

1

**Reference**:

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

## leave a comment

## 0 Comments