If , where , then is equal…

MATHEMATICS · Single correct · CBSE · Mathematics · Trigonometric Functions · Trigonometric Functions

Problem

If

\cos x+\sin x=a

, where

-\frac{\pi}{2}<x<-\frac{\pi}{4}

, then

\cos2x

is equal to (1)

a^2

(2)

a\sqrt{2-a}

(3)

a\sqrt{2+a}

(4)

a\sqrt{2-a^2}

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