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Question: Answered & Verified by Expert
The value of limncosxcosx2cosx4...cosx2n is equal to
MathematicsLimitsJEE Main
Options:
  • A xsinx
  • B sinxx
  • C sin2x2x
  • D 2xsin2x
Solution:
2730 Upvotes Verified Answer
The correct answer is: sin2x2x
Required limit =limncosx20cosx21cosx22...cosx2n
=limn12sinx2ncosx...cosx2n-12sinx2ncosx2n
=limn122sinx2ncosx...2cosx2n-1sinx2n-1
=limn12n+1sinx2n2cosxsinx
=limnsin2x2n+1sinx2n
=sin2x2xlimnx2nsinx2n=sin2x2x

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