Q. 275.0( 1 Vote )

# Mark the Correct alternative in the following:If (2n + 1) x = π, then 2n cos x cos 2x cos22 x ….. cos 2n – 1 x =A.-1B. 1C. 1/2D. None of these

Given (2n – 1) x = π

Then evaluate the expression

2n cos x cos 2x cos22 x ….. cos 2n – 1 x

by taking a 2 from 2n and multiplying and dividing by sin x, we get

[by using the formula sin 2x = 2 sin x cos x]

Now borrowing another 2 from 2n-1

These iterations repeat till we reach the last term

2n x + x = 180°

2n x = 180° - x

So substituting the same in the above solution

So the answer is option B.

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