2.12. Calculating More Trigonometric FunctionsProblemYou want to calculate values for trigonometric functions like sine, tangent, or arccosine. Solution
Perl provides only sub tan { my $theta = shift; return sin($theta)/cos($theta); } The POSIX module provides a wider range of trig functions: use POSIX; $y = acos(3.7); The Math::Trig module provides a complete set of functions and supports operations on or resulting in complex numbers: use Math::Trig; $y = acos(3.7); Discussion
The eval { $y = tan($pi/2); } or return undef; See Also
The 
