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The PHP asin() function is used to return arc sine of a value. The return value will be in the range -𝜋/2 through 𝜋/2.

Note: asin() is the inverse of sin().

Syntax

asin(number)

Parameters

number Required. Specify the value.

Return Value

Returns the arc sine of the value.

Example:

In the below example, asin() function is used to find out the arc sine of a given value.

<?php
  echo asin(0.5)."\n";
  echo asin(1)."\n";
  echo asin(2)."\n";
?>

The output of the above code will be:

0.5235987755983
1.5707963267949
NAN

❮ PHP Math Functions