Q47 / 90 · JEE Main 2024 (30 Jan Shift 1) · Mathematics

If   fx=2cos4x2sin4x3+sin22x3+2cos4x2sin4xsin22x2cos4x3+2sin4xsin22x then 15f'(0) is equal to ________.

  • Correct answer
    A
    0
  • B
    1
  • C
    2
  • D
    6

Solution

Given: fx=2cos4x2sin4x3+sin22x3+2cos4x2sin4xsin22x2cos4x3+2sin4xsin22x

Applying R2→R2-R1, R3→R3-R1

⇒fx=2cos4x2sin4x3+sin22x30-303-3

⇒fx=92cos4x2sin4x3+sin22x10-101-1

⇒fx=92cos4x+2sin4x+3+sin22x

Now, differentiating above function we get,

⇒f'x=98cos3x-sinx+8sin3xcosx+2sin2xcos2x2

⇒f'0=90+0+0

⇒f'0=0

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

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