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SSC CGL 2017 PYQ — Question 88

SSC CGL Tier II Quant - 12/01/2017 • Quantitative Aptitude • Q88

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If cosx.cosy + sinx.siny = – 1 then cosx + cosy is:

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Correct answer: C

Explanation

  The correct answer is option 3 i.e. 0

Application

cosx.cosy + sinx.siny = -1

cos (x – y) = -1

cos (x – y) = Cos 180°

So,

(x – y) = 180°

Suppose x = 180° and y = 0°

So,

cosx + cosy = cos 180° + cos 0° = -1 + 1 = 0