If exp sin2x+sin4x+sin6x+…upto ∞) ln 2} satisfies the equation x2-17x+16=0 then value of 2cosxsinx+2cosx(0
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a
12
b
32
c
52
d
none of these
answer is A.
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Detailed Solution
We have sin2x+sin4x+sin6x+…=sin2x1−sin2x=tan2xTherefore, α=expsin2x+sin4x+sin6x+…upto ∞)ln2} =exptan2xln2=expln2tan2x =2tan2xAs α satisfies the equation x2-17x+16=0 we get α=1 or α=16Since 00 ⇒ α=2tan2x>1. Therefore, 2tan2x=16=24⇒tan2x=4⇒tanx=2[∵tanx>0]Thus, 2cosxsinx+2cosx=2tanx+2=22+2=12