Answer:
steps below
Step-by-step explanation:
sec²θ = 1/cos²θ
sec²θ / (2-sec²θ) = (1/cos²θ) / (2 - 1/cos²θ) = (1/cos²θ) / ((2cos²θ-1)/cos²θ)
==> 1 / (2cos²θ-1) = 1 / (cos²θ - (1-cos²θ)) = 1 / (cos²θ - sin²θ)
==> 1 / cos (2θ)
==> sec (2θ)
If you'd like to prove sec 2θ = right side , just reverse the procedures
