Q24 / 116 · NTA Abhyas (JEE Main) 2020 · Mathematics · Definite Integration

Consider the integral In=∫0π4sin2n−1xsin xdx, then the value of I20-I19 is

  • A
    120
  • Correct answer
    B
    -119
  • C
    -125
  • D
    119

Solution

I 20 − I 19 = ∫ 0 π 4 sin 39x −sin 37x sin x dx
⇒ I 20 − I 19 = ∫ 0 π 4 2sin x cos 38x sin x dx
=sin38x19π40
= sin 38π 4 19
=-119

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

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