SSC CGL Model Paper 19

Question : 60 of 100

Marks: +1, -0

\cos 2 x \cos 2y +

\cos^2(x + y ) - \cos^2(x - y) =?

Solution:

(\cos^2x - \sin^2x) (\cos^2y - \sin^2y)

+ \cos^2 (x + y) -\cos^2 (x - y)

\cos^2x \cos^2y - \sin^2x \cos^2y

- \cos^2x \sin^2y + \sin^2x

\sin^2y + \cos^2 (x + y) - \cos^2(x - y)

\cos^2(x - y) - \sin^2(x + y)

+ \cos^2(x + y)

- \cos^2(x -y)

= \cos2(x + y)

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