1.

If (cosθ + secθ) = 5/2 then(cos2θ + sec2θ) = ?(a) 21/4 (b) 17/4 (c) 29/4 (d) 33/4

Answer»

Correct answer is (b) 17/4

We have (cos θ + sec θ) = 5/2 

Squaring both sides, we get: 

(Cos θ + sec θ)2 = (5/2)2 

⇒ cos2 θ + sec2 θ + 2θ = 25/4 

⇒ cos2 θ + sec2 θ + 2 = 25/4 [∵ sec θ = 1/cos θ] 

⇒ cos2 θ + sec2 θ = 25/4 − 2 = 17/4



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