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TS EAMCET · Maths · Trigonometric Equations

Number of solutions of the equation sinx-sin2x+sin3x=2cos2x-2cosx in 0,π is

  1. A 1
  2. B 3
  3. C 2
  4. D 4
Verified Solution

Answer & Solution

Correct Answer

(B) 3

Step-by-step Solution

Detailed explanation

sinx+sin3x-sin2x=2cos2x-cosx ⇒2sin2x·cosx-sin2x=2cosxcosx-1 ⇒cosx-12sin2x-2cosx=0 ⇒cosx=1 or 2sinx·cosx-cosx=0 cosx=1 or cosx=0 or sinx=12 1) cosx=1, Not possible as x∈0,π 2) cosx=0,x=π2 3) sinx=12,x=π6,5π6
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