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Integrate the functions in Exercises 1 to 24.

    Q18.    \frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}}

Answers (2)

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Given,

\frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}}

Let I = \int \frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}}

We know the identity that

sin (A+B) = sin A cos B + cos A sin B

 

\therefore \frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}} = \frac{1}{\sqrt{\sin^3 x (\sin x \cos \alpha + \cos x \sin \alpha)}}

= \frac{1}{\sqrt{\sin^3 x . \sin x(\cos \alpha + \cot x \sin \alpha)}} = \frac{1}{\sqrt{\sin^4 x (\cos \alpha + \cot x \sin \alpha)}}

\frac{cosec^2 x}{\sqrt{(\cos \alpha + \cot x \sin \alpha)}}

 

 

 

 

 

 

 

 

 

 

 

Posted by

HARSH KANKARIA

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Given,

\frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}}

Let I = \int \frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}}dx

We know 

sin (A+B) = sin A cos B + cos A sin B

 

\therefore \frac{1}{\sqrt{\sin^3 x \sin(x+\alpha)}} = \frac{1}{\sqrt{\sin^3 x (\sin x \cos \alpha + \cos x \sin \alpha)}}

= \frac{1}{\sqrt{\sin^3 x . \sin x(\cos \alpha + \cot x \sin \alpha)}} = \frac{1}{\sqrt{\sin^4 x (\cos \alpha + \cot x \sin \alpha)}}

\frac{cosec^2 x}{\sqrt{(\cos \alpha + \cot x \sin \alpha)}}

Let \\ (\cos \alpha + \cot x \sin \alpha) = t \\ \implies -cosec^2x.\sin \alpha dx = dt

\therefore I =\frac{-1}{sin \alpha} \int \frac{1}{\sqrt{t}}dt

\therefore I =\frac{-2}{sin \alpha} \sqrt{\frac{sin (x+ \alpha)}{sin x}} + C

Posted by

HARSH KANKARIA

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