# ∫ Cos 3 X √ Sin X D X - Mathematics

Sum
$\int\frac{\cos^3 x}{\sqrt{\sin x}} dx$

#### Solution

$\int\frac{\cos^3 x}{\sqrt{\sin x}}dx$
$= \int\frac{\cos^2 x \cdot \cos x}{\sqrt{\sin x}} dx$
$= \int\frac{\left( 1 - \sin^2 x \right) \cos x}{\sqrt{\sin x}}dx$
$Let \sin x = t$
$\Rightarrow \cos x = \frac{dt}{dx}$
$\Rightarrow \text{cos x dx} = dt$
$Now, \int\frac{\left( 1 - \sin^2 x \right) \cos x}{\sqrt{\sin x}}dx$
$= \int\frac{\left( 1 - t^2 \right)}{\sqrt{t}} \cdot dt$
$= \int\left( \frac{1}{\sqrt{t}} - t^\frac{3}{2} \right)dt$
$= \int\left( t^{- \frac{1}{2}} - t^\frac{3}{2} \right)dt$
$= \left[ \frac{t^{- \frac{1}{2} + 1}}{- \frac{1}{2} + 1} - \frac{t^\frac{3}{2} + 1}{\frac{3}{2} + 1} \right] + C$
$= 2\sqrt{t} - \frac{2}{5} t^\frac{5}{2} + C$
$= 2\sqrt{\sin x} - \frac{2}{5} \ sin^\frac{5}{2} x + C$

Concept: Indefinite Integral Problems
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#### APPEARS IN

RD Sharma Class 12 Maths
Chapter 19 Indefinite Integrals
Exercise 19.9 | Q 13 | Page 58