MCQ
$\int_{}^{} {\frac{{\sin x\cos x}}{{a{{\cos }^2}x + b{{\sin }^2}x}}dx = } $
  • $\frac{1}{{2(b - a)}}\log (a{\cos ^2}x + b{\sin ^2}x) + c$
  • B
    $\frac{1}{{b - a}}\log (a{\cos ^2}x + b{\sin ^2}x) + c$
  • C
    $\frac{1}{2}\log (a{\cos ^2}x + b{\sin ^2}x) + c$
  • D
    None of these

Answer

Correct option: A.
$\frac{1}{{2(b - a)}}\log (a{\cos ^2}x + b{\sin ^2}x) + c$
a
(a) Put $a{\cos ^2}x + b{\sin ^2}x = t$$ \Rightarrow 2(b - a)\sin x\cos x = dt,$
then $\int_{}^{} {\frac{{\sin x\cos x\,dx}}{{a{{\cos }^2}x + b{{\sin }^2}x}} = \frac{1}{{2(b - a)}}\int_{}^{} {\frac{1}{t}\,dt} } $
$ = \frac{1}{{2(b - a)}}\log (a{\cos ^2}x + b{\sin ^2}x) + c$.

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