1.

Given that sinθ = a/b , then cosθ is equal to(A) b/√(b2– a2) (B) b/a (C) √(b2-a2)/b (D) a/√(b2-a2)

Answer»

(C) √(b2-a2)/b

According to the question,

sin θ =a/b

We know, sin2 θ +cos2 θ =1

sin2 A = 1-cos2 A

sin A = √(1-cos2 A

So, cos θ = √(1-a2/b2 ) = √((b2-a2)/b2 ) = √(b2-a2 )/b

Hence, cos θ = √(b2 – a2 )/b



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