To find the arcsine, or inverse sine, of a number, we can use the php **asin()** function.

`asin(x)`

In php, we can easily use trigonometric functions from the collection of php math functions. These php math functions allow us to perform trigonometry easily.

To find the arcsine of a number, we use the php **asin()** function.

Below is the php syntax to find the inverse sine of a number.

`asin(x)`

The input to the **asin()** function must be a float between -1 and 1. The return value will be a float between -pi/2 and pi/2 radians.

```
echo asin(0.5); // 0.5235987755982989
echo asin(0); // 0.0
echo asin(-0.75); // -0.848062078981481
```

## Finding the Inverse Sine of a Number in php

Arcsine is defined as the inverse of the sine of a number.

Below, we show that if we pass a number to **sin()** and then call the php **asin()** function, we get back the same number.

```
echo asin(sin(pi()/3)); // 1.0471975511965976
echo pi()/3; // 1.0471975511965976
```

Hopefully this article has been beneficial for you to understand how to use the **asin()** function in php to find the arcsine of a number.

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