MCQ
$\int \frac{1}{\cos x-\cos ^2 x} \cdot d x=$
  • A
    $\log (\operatorname{cosec} x-\cot x)+\tan \left(\frac{x}{2}\right)+c$
  • B
    sin 2x – cos x + c
  • $\log (\sec x+\tan x)-\cot \left(\frac{x}{2}\right)+c$
  • D
    cos 2x – sin x + c

Answer

Correct option: C.
$\log (\sec x+\tan x)-\cot \left(\frac{x}{2}\right)+c$
$\log (\sec x+\tan x)-\cot \left(\frac{x}{2}\right)+c$

Hint : $\int \frac{1}{\cos x-\cos ^2 x} d x$

$=\int \frac{1}{\cos x(1-\cos x)} d x$

$=\int \frac{(1-\cos x)+\cos x}{\cos x(1-\cos x)} d x$

$=\int\left[\sec x+\frac{1}{2} \operatorname{cosec}^2\left(\frac{x}{2}\right)\right] d x$

$=\log |\sec x+\tan x|+\frac{1}{2} \frac{\left(-\cot \frac{x}{2}\right)}{1 / 2}+c$

$=\log |\sec x+\tan x|-\cot \left(\frac{x}{2}\right)+c$

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