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PHP Math - asin() Function

The PHP Math asin() function returns arc sine of a value. The return value will be in the range -𝜋/2 through 𝜋/2. In special cases it returns the following:

  • If the argument is NAN or its absolute value is greater than 1, then the result is NAN.

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




number Required. Specify the value.

Return Value

Returns the arc sine of the value.


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

echo "asin(-1) = ".asin(-1)."\n";
echo "asin(-0.5) = ".asin(-0.5)."\n";
echo "asin(0) = ".asin(0)."\n";
echo "asin(0.5) = ".asin(0.5)."\n";
echo "asin(1) = ".asin(1)."\n";
echo "asin(2) = ".asin(2)."\n";
echo "asin(NAN) = ".asin(NAN)."\n";

The output of the above code will be:

asin(-1) = -1.5707963267949
asin(-0.5) = -0.5235987755983
asin(0) = 0
asin(0.5) = 0.5235987755983
asin(1) = 1.5707963267949
asin(2) = NAN
asin(NAN) = NAN

❮ PHP Math Functions