MCQ
Choose the correct option from given four options : $\int\frac{\cos2\text{x}-\cos2\theta}{\cos\text{x}-\cos\theta}\text{dx}$ is equal to :
  • $2(\sin+\text{x}\cos\theta)+\text{C}$
  • B
    $2(\sin-\text{x}\cos\theta)+\text{C}$
  • C
    $2(\sin+2\text{x}\cos\theta)+\text{C}$
  • D
    $2(\sin-2\text{x}\cos\theta)+\text{C}$

Answer

Correct option: A.
$2(\sin+\text{x}\cos\theta)+\text{C}$
Let $\text{I}=\int\frac{\cos2\text{x}-\cos2\theta}{\cos\text{x}-\cos\theta}\text{dx}$
$=\int\frac{\big(2\cos^2\text{x}-1-2\cos^2\theta+1)}{\cos\text{x}-\cos\theta}\text{dx}$
$=2\int\frac{\big(\cos\text{x}+\cos\theta)(\cos\text{x}-\cos\theta)}{\cos\text{x}-\cos\theta}\text{dx}$
$=2\int(\cos\text{x}+\cos\theta)\text{dx}$
$=2(\sin\text{x}+\text{x}\cos\theta)+\text{C}$

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