Quadruple Angle Formulas

Quadruple Angle Formula for Tangent
where $\sin, \cos, \tan$ denote sine, cosine and tangent respectively.

Quadruple Angle Formula for Hyperbolic Tangent
where $\sinh, \cosh, \tanh$ denote hyperbolic sine, hyperbolic cosine and hyperbolic tangent respectively.

Also see

 * Triple Angle Formulas
 * Quintuple Angle Formulas