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Need solution for RD Sharma Maths Class 12 Chapter 18 Indefinite Integrals Excercise Very Short Answers Question 42

Answers (1)

Answer: 2\sin\sqrt{x}+c

Hint: You must know about the integral rule of trigonometric functions

Given: \int \frac{\cos \sqrt{x}}{\sqrt{x}}dx

Solution:

\int \frac{\cos \sqrt{x}}{\sqrt{x}}dx

Let

\begin{aligned} &t=\sin \sqrt{x}\\ &d t=\frac{\cos \sqrt{x}}{2 \sqrt{x}} d x\\ &2 d t=\frac{\cos \sqrt{x}}{\sqrt{x}} \quad\quad\quad\quad\quad\quad\quad\quad\quad\left[\frac{d}{d x} \sin x=\cos x\right] \end{aligned}

 \begin{aligned} \int \frac{\cos \sqrt{x}}{\sqrt{x}} d x &=\int 2 d t \\ &=2 \mathrm{t}+\mathrm{c} \quad\quad\quad\quad\quad\quad\quad\quad\left[\int x^{n} d x=\frac{x^{n+1}}{n+1}\right] \\ &=2 \sin \sqrt{x}+\mathrm{c} \end{aligned}                                        

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