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If f(x) = cosx. cos2x. Cos4x. Cos8x.cos1...

If f(x) = cosx. cos2x. Cos4x. Cos8x.cos16x, then f '(pi/4) is :

A

`sqrt2`

B

`1/sqrt2`

C

1

D

none of these

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The correct Answer is:
A
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PATHFINDER-APPLICATION OF DERIVATIVE-QUESTION BANK
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