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PHP | cos( ) Function
• Last Updated : 09 Mar, 2018

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:

`float cos(\$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:
 `      `

Output:

`-0.98999249660045`
• Passing -3 as a parameter:
 `      `

Output:

`-0.98999249660045`
• When (2*M_PI) is passed as a parameter, M_PI is a constant in PHP whose value is 3.1415926535898:
 `      `

Output:

`1`
• Passing 0 as a parameter:
 `      `

Output:

`1`

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