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 *sin()*function in PHP is used to find the sine value of a number.

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

**Syntax:**

floatsin($value)

**Parameters:** This function accepts a single parameter *value*. It is the number whose sine 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 sine value of number passed to it as argument.

Examples:

Input : sin(3) Output : 0.14112000805987 Input : sin(-3) Output : -0.14112000805987 Input : sin(2*M_PI) Output : 1 Input : sin(0) Output : 0

Below programs illustrate sin() function in PHP:

- Passing 3 as a parameter:
`<?`

`php`

`echo (sin(3));`

`?>`

Output:

0.14112000805987

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

`php`

`echo (sin(-3));`

`?>`

Output:

-0.14112000805987

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

`php`

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

`?>`

Output:

1

- Passing 0 as a parameter:
`<?`

`php`

`echo (sin(0));`

`?>`

Output:

0

**Reference**:

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

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