Programming Perl, 4th Edition

sin

sin EXPR
sin

Sorry, there’s nothing wicked about this operator. It merely returns the sine of EXPR (expressed in radians).

For the inverse sine operation, you may use Math::Trig or the POSIX module’s asin function, or use this relation:

sub asin { atan2($_[0], sqrt(1 – $_[0] * $_[0])) }