Question

it is tan²thetha at RHS​

Answer 1

Answer:

Hello mate!

sec^6 θ = (sec²θ)³ = (1 + tan²θ)³

(1 + tan²θ)³ = (1)³ + (tan²θ)³ + 3 × 1 × tan²θ (1 + tan²θ)

1 + tan^6 + 3 tan²θ sec²θ

Hence proved..   ;)