Question

Prove that cos2theta (1+tan2theta)=1

Answer 1

step-by-step explanation:

given

cos²θ(1+tan²θ)=1

L.H.S

cos²θ(1+tan²θ)

=cos²θsec²θ  [sec²θ+tan²θ=1      ∴sec²θ=1+tan²θ]

=cos²θ*1/cos²θ

=1 = R.H.S