Q1 of 62 Page 81

Prove that

We know that-


2 cos x cos y = cos(x + y) + cos(x - y)


Putting x = (9π/13) and y = (π/13) in (1), we get-


…(1)


∴ L.H.S


[From (1)]







since cos (π/2) = 0


∴ L.H.S = 0 + 0 = 0 = R.H.S


Hence, L.H.S = R.H.S…Proved


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