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The asin() function in PHP returns the arc sine (inverse sine) of a number.
It accepts a value between -1 and 1 and returns the angle in radians.
The result lies between -π/2 and +π/2 radians.
Useful for trigonometric calculations, especially in geometry or physics.
You can convert the result to degrees using rad2deg().

Syntax

asin(float $num): float

• $num: A float value between -1 and 1
• Returns: The angle in radians, ranging from -π/2 to +π/2

File Name: asin-example.php

<!--?php echo asin(0); // ➤ 0 echo "\n"; echo asin(1); // ➤ 1.5707963267949 (π/2 radians) echo "\n"; echo asin(-1); // ➤ -1.5707963267949 (-π/2 radians) ?-->

Convert Radians to Degrees

$angle = asin(0.5);               // Returns radians
$degrees = rad2deg($angle);       // ➤ 30
echo $degrees;

Use Cases