You are viewing the version of this documentation from Perl 5.24.0. View the latest version
cos EXPR
cos

Returns the cosine of EXPR (expressed in radians). If EXPR is omitted, takes the cosine of $_.

For the inverse cosine operation, you may use the Math::Trig::acos function, or use this relation:

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