Answer:
Step-by-step explanation:
Simplify RHS
Cotx +2tanx+tan^3x
Cotx/sinx+2(sinx/cosx)+sin^3x/cos^3x
Taking LCM
(cos^4x+2sin^2xcos^2x+sin^4x)/sinx cos^3x
(Cos^2x+sin^2x)^2/sinx cos^3x
(1/sinx cos^3x)
(1/sinx cos^3x)*(cosx/cosx)
Cotx sec^4x
LHS=RHS
Hence proved
