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Need solution for RD Sharma maths class 12 chapter Indefinite Integrals exercise 18.8 question 19

Answers (1)

Answer:

        \frac{1}{b-a}In\left | a\: cos^{2}\: x+b\: sin^{2}\: x \right |+C

Hint:

        \int \! \frac{dt}{t}=log\left | t \right |+C

Given:

        \int \! \frac{sin\: 2x}{a\: cos^{2}\: x+b\: sin^{2}x}dx            ........(1)

Explanation:

Let

        a\: cos^{2}\: x+b\: sin^{2}x=t

        (2a\, cos\, x(-sin\, x)+b(2\, sin\, x)(cos\, x))dx=dt

        (b-a)[2\, cos\, x\, sin\, x]dx=dt

        (b-a)sin\, 2x\, dx=dt

        sin\, 2x\, dx=\frac{dt}{b-a}

Put in (1)

        \frac{1}{b-a}\int \! \frac{dt}{t}

        =\frac{1}{b-a}In\left | t \right |+C

        =\frac{1}{b-a}In\left | a\: cos^{2}\: x+b\: sin^{2} \right |+C

 

Posted by

Gurleen Kaur

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