If cosθ + sec θ = 12 , find the value of cos2θ + sec2θ.
Answer & explanation
Correct answer: option 2
Formula I → [ cosθ = \(\frac{1}{secθ}\)] and vice versa.
Formula II → [If x + \(\frac{1}{x}\) = n and x2 + \(\frac{1}{x^2}\) = n2 - 2 ]
cosθ + \(\frac{1}{cosθ}\) = 12
⇒ cos2θ + \(\frac{1}{cos^2θ}\) = (12)2 - 2
⇒ cos2θ + sec2θ = 144 - 2 = 142