1.

If cos θ = \(\frac {3}{4}\) then value of cos 2θ is ___________(a) \(\frac {1}{6}\)(b) \(\frac {1}{4}\)(c) \(\frac {1}{8}\)(d) \(\frac {3}{8}\)This question was addressed to me in semester exam.My doubt is from Trigonometric Ratios in chapter Trigonometry of Mathematics – Class 10

Answer»

Right option is (C) \(\frac {1}{8}\)

BEST explanation: COS 2θ = 2cos θ^2 – 1

cos θ = \(\frac {3}{4}\)

cos 2θ = 2(\(\frac {3}{4}\))^2 – 1

= \(\frac {1}{8}\)



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