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Need solution for RD Sharma maths class 12 chapter Indefinite Integrals exercise 18.8 question 31

Answers (1)

Answer:

        log\left | log(sec\, x+tan\, x) \right |+C

Hint:

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

Given:

        \int \! \frac{sec\, x}{log(sec\, x+tan\, x)}dx                ......(1)

Explanation:

Let

        log(sec\, x+tan\, x)=t

        \frac{1}{sec\, x+tan\, x}(sec\, x\: tan\, x+sec^{2}x)dx=dt

        \Rightarrow \frac{\frac{sin\, x}{cos^{2}x}+\frac{1}{cos^{2}x}}{\frac{sin\, x}{cos\, x}+\frac{1}{cos\, x}}dx=dt

        \Rightarrow \frac{\frac{1+sin\, x}{cos^{2}x}}{\frac{1+sin\, x}{cos\, x}}dx=dt

        =sec\, xdx=dt

Put in (1)

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

        =log\left | log(sec\, x+tan\, x) \right |+C

Posted by

Gurleen Kaur

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