=over

=item sin EXPR
X<sin> X<sine> X<asin> X<arcsine>

=item sin

Returns the sine of EXPR (expressed in radians).  If EXPR is omitted,
returns sine of L<C<$_>|perlvar/$_>.

For the inverse sine operation, you may use the C<Math::Trig::asin>
function, or use this relation:

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

=back