Q44 / 83 · NTA Abhyas (JEE Main) 2020 · Mathematics · Trigonometric Equations

The solution set of x∈-π,π for the inequality sin⁡2x+1≤cos⁡x+2sin⁡x is

  • A
    x∈0,π6
  • Correct answer
    B
    x∈π6,5π6∪0
  • C
    x∈-π6,5π6
  • D
    x∈-π2,π2

Solution

2sin⁡xcos⁡x+1-cos⁡x-2sin⁡x≤0
2sin⁡x-1cos⁡x-1≤0
Case I: cos⁡x=1⇒x=0
Case II: otherwise cos⁡x<1
⇒2sin⁡x-1≥0⇒sin⁡x≥12
⇒x∈π6,5π6
Hence, from case I and case II,
x∈π6,5π6∪0

Hence, the correct answer is option: 'B'.

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