TrigExpand[expr] expands out trigonometric functions in expr.
TrigExpand operates on both circular and hyperbolic functions.
TrigExpand splits up sums and integer multiples that appear in arguments of trigonometric functions, and then expands out products of trigonometric functions into sums of powers, using trigonometric identities when possible.
See Section 1.4.5 and Section 3.3.7.
See also: TrigFactor, TrigReduce, TrigToExp, Expand, FunctionExpand, Simplify, FullSimplify.
New in Version 3.