PHP in a Nutshell

Name

asin()

Synopsis

    float asin ( float num )

The asin() function calculates the arc sine value of the number provided as its only parameter, essentially reversing the operation of sine(). The return value is in radians—you should use the rad2deg() to convert radians to degrees.

    $asin1 = asin(0.4346);
    $asin2 = asin(sin(80));