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SSC CHSL 2023 PYQ — Question 27

SSC CHSL Tier II - 26 Jun 2023 - Shift 1 • Quantitative Aptitude • Q27

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If Sin x + Sin2x = 1, then what is the value of Cos8x + 2 Cos6x + cos4x?

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Correct answer: D

Explanation

The correct answer is option 4 i.e. 1

sin x + sin2x = 1

sin x = 1 - sin2x

sin x = cos2x

sin x + sin2x = 1

Squaring both sides -

sin2x + 2sin2x + sin2x = 1

{Putting cos2x = sinx}

cos8x + 2cos6x + cos4x = 1