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SSC CGL 2020 PYQ — Question 25

SSC CGL Tier II - Quant - 18 Nov 2020 • Quantitative Aptitude • Q25

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If sin (x + y) = cos(x - y), then the value of cos2x is :

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Correct answer: A

Explanation

The correct answer is option 1 i.e. 12\frac{1}{2}

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

sin(x + y) = sin(90 - x + y)

x + y = 90 - x + y

2x = 90

x = 45

cos2x =  cos245 = 1/2.