Q8 / 104 · NTA Abhyas (JEE Main) 2020 · Mathematics · Indefinite Integration

Consider the integrals I=∫sin⁡x3cos⁡x+4sin⁡xdx and J=∫cos⁡x3cos⁡x+4sin⁡xdx. Then, the integral 4J-3I is equal to (where, c is the constant of integration)

  • A
    ln⁡3cos⁡x-4sin⁡x+c
  • Correct answer
    B
    ln⁡3cos⁡x+4sin⁡x+c
  • C
    ln⁡3sin⁡x+4cos⁡x+c
  • D
    ln⁡3sin⁡x-4cos⁡x+c

Solution

4J-3I=∫4cos⁡x-3sin⁡x3cos⁡x+4sin⁡xdx
Let, 3cos⁡x+4sin⁡x=t
⇒4cos⁡x-3sin⁡xdx=dt
⇒4J-3I=∫dtt=ln⁡t+c
⇒4J-3I=ln⁡3cos⁡x+4sin⁡x+c

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

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