Trigonometrical Ratios and Identities 1 Question 6

6. The value of cosπ22cosπ23cosπ210sinπ210 is

(a) 11024

(b) 12

(c) 1512

(d) 1256

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Answer:

Correct Answer: 6. (a, b, c, d)

Solution:

  1. We know that, cosαcos(2α)cos(22α)cos(2n1α)=sin(2nα)2nsinα

cosπ22cosπ23cosπ210sinπ210

=sinπ2102929sinπ210sinπ210[ here,α=π210 and n=9]

=129sinπ2=129=1512



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