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Provide Solution For R.D. Sharma Maths Class 12 Chapter 18  Indefinite Integrals Exercise  Multiple Choice Questions Question 29 Maths Textbook Solution.

Answers (1)

Answer:

\sin x+C

Given:

\int x \sin x d x=-x \cos x+\alpha

Hint:

You must know the derivation of sin x and rule to integrate by parts.

Explanation:

Let I=\int x \sin x d x

          =x(-\cos x)+\int(1) \cos x d x                              \text { [ : :Integration by parts } \left.\int u . v d x=u \int v d x-\int \frac{d u}{d x} \int v d x d x\right]

          =-x \cos x+\sin x+C

Acc. to given              

\begin{aligned} &I=-x \cos x+\alpha \\ &\Rightarrow-x \cos x+\sin x+C=-x \cos x+\alpha \end{aligned}

Comparing both sides

We get,\alpha=\sin x+C

               

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