Explanation
Consider the given integral.
$$I=\int{\dfrac{x}{\sqrt{{{x}^{2}}+2}}dx}$$
Let $$t={{x}^{2}}+2$$
$$ \dfrac{dt}{dx}=2x+0 $$
$$ \dfrac{dt}{2}=xdx $$
Therefore,
$$ I=\dfrac{1}{2}\int{\dfrac{dt}{\sqrt{t}}} $$
$$ I=\dfrac{1}{2}\left( 2\sqrt{t} \right)+C $$
$$ I=\sqrt{t}+C $$
On putting the value of $$t$$, we get
$$I=\sqrt{{{x}^{2}}+2}+C$$
Hence, this is the answer.
$$ I=\int{\sqrt{\dfrac{a+x}{a-x}}dx} $$
$$ I=\int{\sqrt{\dfrac{a+x}{a-x}}\times \sqrt{\dfrac{a+x}{a+x}}dx} $$
$$ I=\int{\dfrac{a+x}{\sqrt{{{a}^{2}}-{{x}^{2}}}}dx} $$
$$ I=a\int{\dfrac{1}{\sqrt{{{a}^{2}}-{{x}^{2}}}}dx}-\dfrac{1}{2}\int{\dfrac{-2x}{\sqrt{{{a}^{2}}-{{x}^{2}}}}dx} $$
$$ I=a{{\sin }^{-1}}\left( \dfrac{x}{a} \right)-\dfrac{1}{2}\int{\left\{ \dfrac{d}{dx}\left( {{a}^{2}}-{{x}^{2}} \right){{\left( {{a}^{2}}-{{x}^{2}} \right)}^{-1/2}} \right\}dx} $$
$$ I=a{{\sin }^{-1}}\left( \dfrac{x}{a} \right)-\dfrac{1}{2}\dfrac{{{\left( {{a}^{2}}-{{x}^{2}} \right)}^{1/2}}}{\left( 1/2 \right)}+C $$
$$ I=a{{\sin }^{-1}}\left( \dfrac{x}{a} \right)-\sqrt{{{a}^{2}}-{{x}^{2}}}+C $$
Hence, this is the correct answer.
Consider the following integral.
$$ \int\limits_{{}}^{{}}{\dfrac{{{2}^{x}}}{\sqrt{1-{{4}^{x}}}}}dx $$
Solution:
Let and differentiate w.r.t “x” we get.
$$ t={{2}^{x}} $$
$$ \dfrac{dt}{dx}={{2}^{x}}\ln 2 $$
$$ \int\limits_{{}}^{{}}{\dfrac{{{2}^{x}}}{\sqrt{1-{{4}^{x}}}}}dx\,\,\,\,\,\,\,\,......\left( 1 \right)\ $$
Put the value \[dx\,\,\] of in eq . (1) we get.
$$ =\int\limits_{{}}^{{}}{\dfrac{{{2}^{x}}}{\sqrt{1-{{4}^{x}}}}}dx\,\,\,\,\,\,\,\,......\left( 1 \right) $$
$$ =\int\limits_{{}}^{{}}{\dfrac{{{2}^{x}}}{{{2}^{x}}\ln 2\sqrt{1-{{\left( {{t}^{2}} \right)}^{x}}}}}dx $$
$$ =\int\limits_{{}}^{{}}{\dfrac{1}{\ln 2\sqrt{1-{{\left( {{t}^{2}} \right)}^{x}}}}}dx\, $$
$$ =\dfrac{1}{\ln 2}{{\sin }^{-1}}x+C $$
Hence, the value of $$[K=\dfrac{1}{\ln 2}]$$
Hence, this is the correct answer .
$$ I=\int_{1}^{e}{\dfrac{dx}{\ln \left( {{x}^{x}}\cdot {{e}^{x}} \right)}} $$
$$ I=\int_{1}^{e}{\dfrac{dx}{\ln {{x}^{x}}+\ln {{e}^{x}}}} $$
$$ I=\int_{1}^{e}{\dfrac{dx}{x\ln x+x\ln e}} $$
$$ I=\int_{1}^{e}{\dfrac{dx}{x\ln x+x}} $$
$$ I=\int_{1}^{e}{\dfrac{dx}{x\left( \ln x+1 \right)}} $$
Let $$t=\ln x+1$$
$$ \dfrac{dt}{dx}=\dfrac{1}{x}+0 $$
$$ dt=\dfrac{dx}{x} $$
$$ I=\int_{1}^{2}{\dfrac{dt}{t}} $$
$$ I=\left[ \ln \left( t \right) \right]_{1}^{2} $$
$$ I=\ln \left( 2 \right)-\ln \left( 1 \right) $$
$$ I=\ln 2 $$
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