FullSimplify

FullSimplify[expr] tries a wide range of transformations involving elementary and special functions to find the simplest form.

Examples

Simplify with special functions:

FullSimplify[Sin[x]^2 + Cos[x]^2]
(* 1 *)

Simplify complex expressions:

FullSimplify[Gamma[n + 1]/Gamma[n], n > 0]
(* n *)

With assumptions:

FullSimplify[Log[Exp[x]], x \[Element] Reals]
(* x *)

Please visit the official Wolfram Language Reference for more details.