Number of solution(s) satisfying the equation 1sinx−1sin2x=2sin4x in [0,4π] is equal to
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a
0
b
2
c
4
d
6
answer is C.
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Detailed Solution
1sinx−1sin2x=2sin4x⇒ sin2x−sinxsinxsin2x=22sin2xcos2x⇒ 2sin2xcos2x−2sinxcos2x=2sinx⇒ sin4x−sin3x+sinx=2sinx⇒ sin4x=sin3x+sinx⇒ 2sin2xcos2x=2sin2xcosx⇒ 2x=2nπ±x (as x=2kπ is not in domain) ⇒ x=2nπ3,n∈I ( as sin2x≠0)⇒n=1,2,4,5,….Thus, four solutions are 2π3,4π3,8π3,10π3