Thursday, 20 August 2015

`int dx/(x(sqrt(4x^2-1)))` Find the indefinite integral

We have to evaluate the integral : ```\int \frac{dx}{x\sqrt{4x^2-1}}`


Let `\sqrt{4x^2-1}=u`


So, `\frac{1}{2\sqrt{4x^2-1}}.8x dx=du`


      `\frac{4xdx}{\sqrt{4x^2-1}}=du`


       `\frac{dx}{\sqrt{4x^2-1}}=\frac{du}{4x}`



Hence we have,


`\int \frac{dx}{x\sqrt{4x^2-1}}=\int \frac{du}{4x^2}`


                 `=\int \frac{du}{u^2+1}`


                  `=tan^{-1}(u)+C`


                   `=tan^{-1}(\sqrt{4x^2-1})+C` where C is a constant


We have to evaluate the integral : ```\int \frac{dx}{x\sqrt{4x^2-1}}`


Let `\sqrt{4x^2-1}=u`


So, `\frac{1}{2\sqrt{4x^2-1}}.8x dx=du`


      `\frac{4xdx}{\sqrt{4x^2-1}}=du`


       `\frac{dx}{\sqrt{4x^2-1}}=\frac{du}{4x}`



Hence we have,


`\int \frac{dx}{x\sqrt{4x^2-1}}=\int \frac{du}{4x^2}`


                 `=\int \frac{du}{u^2+1}`


                  `=tan^{-1}(u)+C`


                   `=tan^{-1}(\sqrt{4x^2-1})+C` where C is a constant


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