Let S = x ∈ - π ,   π : x ≠ 0 ,   ± π 2 . The sum of all distinct…

Let S=x-π, π:x0, ±π2 . The sum of all distinct solution of the equation 3secx+cosec x+2tanx-cotx=0, in the set S is equal to 
  1. -7π9
  2. -2π9
  3. 0
  4. 5π9

Solution

3Cosx+1Sinx+2 Sinxcosx-Cosxsinx=0
3sinx+cosx=2cos2x
cos2x=cosx-π3
2x=2nπ±x-π3,2x=2nπ+xπ32x=2nπx+π3
⇒ x=6n-1π3 or 6n+1π9
x= -π3,π9,7π9 and -5π9 in -π, π
 sum = 0

Asked in: JEE Advanced 2016 (Paper 1)

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