Concept Used: - A.M ≥ G.M - If a and b are two numbers then (a+b)∕2≥√ab - cos2x×sec2x=1 Calculation: We have y=cos2x+sec2x−⋯ (i) Let the two numbers be cos2x and sec2x According to the concept used A. M≥G.M ⇒[cos2x+sec2x]∕2≥√[cos2x×sec2x] ⇒[cos2x+sec2x]∕2≥1 ⇒[cos2x+sec2x]≥2 Now, from (i) ⇒y≥2 ∴ The correct relation is y≥2.