Prove: tan(π+4x)=(4 tanx-4 tan^3 x)/(tan^4 x-6 tan^2 x+1)
tan(π+4x) = (tanπ + tan4x)/(1 - tanπ tan4x) = tan4x
tan2x = 2tanx / (1-tan^2 x)
tan4x = 2tan2x/(1-tan^2 2x) = 4tanx/[1-tan^2 x)(1 - tan^2 2x)]
see what you can do with that
tan2x = 2tanx / (1-tan^2 x)
tan4x = 2tan2x/(1-tan^2 2x) = 4tanx/[1-tan^2 x)(1 - tan^2 2x)]
see what you can do with that