This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.
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Trigonometric Functions
With careful attention to branch cuts, Mathematica supports trigonometric functions everywhere in the complex plane, with extensive exact and algebraic transformations, together with efficient arbitrary-precision numerical evaluation. Mathematica follows the standard mathematical convention of using radians for trigonometric function arguments.
Sin  ▪ Cos  ▪ Tan  ▪ Csc  ▪ Sec  ▪ Cot

Degree (°) — constant to convert from radians to degrees
I () — , entered as Esc ii Esc ("imaginary i")
FromDMS, DMSList convert between radians and degrees, minutes, seconds

FullSimplify simplify trigonometric expressions
FunctionExpand reduce to algebraic forms or simpler arguments

TrigExpand etc.
TrigFactor Sin[..]+Sin[..]product of terms, etc.
TrigReduce etc.
TrigToExp, ExpToTrig convert between trigonometric functions and exponentials
ComplexExpand expand into real and imaginary parts

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