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AP EAMCET · Maths · Indefinite Integration

If cos4x+1cotx-tanx=kcos4x+c, then "k" is equal to

  1. A -12
  2. B -18
  3. C -13
  4. D -15
Verified Solution

Answer & Solution

Correct Answer

(B) -18

Step-by-step Solution

Detailed explanation

∫cos4x+1cotx-tanx =∫cos4x+1cos2x-sin2xcosxsinx Use:  cos2x=2cos2x-1=1-2sin2x =∫2cos22xcos2x×sinxcosxdx =12∫2cos2xsin2xdx =12∫sin4xdx =12×-cos4x4+c =-18cos4x+c ⇒ k=-18