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How can I get sine, cosine, and tangent to return values in degrees?

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Contributed by dooberwah on Dec 21, 2002 at 21:24 UTC
Q&A  > math


Answer: How can I get sine, cosine, and tangent to return values in degrees?
contributed by tachyon

The perl sin and cos functions take arguments in the form of radians (rather than degrees). 180 degrees = Pi radians so both radians and degrees are measures of angle. You question has no answer per se as sin and cos do not return values that can be expressed as any measure of angle like radians or degrees. Hopefully this code covers what you want. The asin, acos and atan functions return radians and are the inverse functions of sin, cos and tan respectively:

my $pi = 3.14159265358979; sub deg_to_rad { ($_[0]/180) * $pi } sub rad_to_deg { ($_[0]/$pi) * 180 } sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) } sub acos { atan2( sqrt(1 - $_[0] * $_[0]), $_[0] ) } sub tan { sin($_[0]) / cos($_[0]) } sub atan { atan2($_[0],1) }; print 'sin 30 degrees is ', sin(deg_to_rad(30)), "\n"; print 'inverse sin 0.5 is ', rad_to_deg(asin(0.5)), ' degrees';
Answer: How can I get sine, cosine, and tangent to return values in degrees?
contributed by tachyon

Just uploaded Math::Trig::Degree which will do both degrees and radians.

Answer: How can I get sine, cosine, and tangent to return values in degrees?
contributed by barrachois

Rather than have a line like this

my $pi = 3.14159265358979;
which requires you to choose how many digits of pi you (or your operating system) want, and even may require (for some, at least) that you look up the value of pi, I would suggest that a line like this instead will do the right thing.
my $pi = 4*atan2(1,1);

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