MCQ
$\int_{}^{} {\frac{{\cos {\rm{ec}}x}}{{\log \tan \frac{x}{2}}}\;dx = } $
  • $\log \left( {\log \tan \frac{x}{2}} \right) + c$
  • B
    $2\log \left( {\log \tan \frac{x}{2}} \right) + c$
  • C
    $\frac{1}{2}\log \left( {\log \tan \frac{x}{2}} \right) + c$
  • D
    None of these

Answer

Correct option: A.
$\log \left( {\log \tan \frac{x}{2}} \right) + c$
a
(a) $\log \tan \frac{x}{2} = t $  $ \Rightarrow \frac{1}{{\tan \frac{x}{2}}}.\frac{1}{2}{\sec ^2}\frac{x}{2}\,dx = dt$
$ \Rightarrow {\rm{cosec}}\,x\,dx = dt,$
 therefore $\int_{}^{} {\frac{{{\rm{cosec}}\,x}}{{\log \tan \frac{x}{2}}}\,dx} = \int_{}^{} {\frac{1}{t}dt} = \log t + c = \log \left( {\log \tan \frac{x}{2}} \right) + c$.

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