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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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cos EXPR


Returns the cosine of EXPR (expressed in radians). If EXPR is omitted, takes 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] ) }
ISBN 9781906966027Perl Language Reference ManualSee the print edition