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Class 12 Integrals · Short Answer2 Marksindefinite_integration

Class 12 Maths · Integrals · Short Answer #140

Evaluate \(\int \frac{x}{x \tan{\left(x \right)} + 1}\,dx\). Work on intervals with cos x≠0 and 1+x tan x≠0.

✅ Step-by-Step Solution

Final Answer: \(\log{\left(\left|{x \sin{\left(x \right)} + \cos{\left(x \right)}}\right| \right)}\) + C
  1. Let D=cos x+x sin x. Its derivative is D′=x cos x.
  2. Where the original integrand is defined, x/(1+x tan x)=x cos x/D=D′/D. Integrate as ln|D|.
  3. Therefore the required integral is \(\log{\left(\left|{x \sin{\left(x \right)} + \cos{\left(x \right)}}\right| \right)}\) + C.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] Let D=cos x+x sin x. Its derivative is D′=x cos x.
  • [1 mark] Where the original integrand is defined, x/(1+x tan x)=x cos x/D=D′/D. Integrate as ln|D|.
  • [0.5 marks] Therefore the required integral is \(\log{\left(\left|{x \sin{\left(x \right)} + \cos{\left(x \right)}}\right| \right)}\) + C.

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