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If the solution curve of the differential equation \mathrm{\left(\left(\tan ^{-1} y\right)-x\right) d y=\left(1+y^{2}\right) d x} passes through the point \mathrm{\left ( 1,0 \right )}, then the abscissa of the point on the curve whose ordinate is \mathrm{\tan(1)}, is

Option: 1

\mathrm{2e}


Option: 2

\mathrm{\frac{2}{e}}


Option: 3

\mathrm{2}


Option: 4

\mathrm{\frac{1}{e}}


Answers (1)

best_answer

\mathrm{\frac{d x}{d y}+\frac{x}{1+y^{2}}=\frac{\tan ^{1} y}{1+y^{2}}}

Linear differential equation

Integral factor

\mathrm{\text { If }=e^{\int \frac{1}{1+y^{2}} d y}=e^{\tan ^{-1} y}} \\

\mathrm{\Rightarrow \quad x \times e^{\tan ^{-1} y}=\int \frac{\tan ^{-1} y e^{\tan ^{-1} y}}{1+y^{2}} d y}

Let  \mathrm{\tan ^{-1} y=t \rightarrow x \times e^{\tan ^{-1} y}=\int \frac{t}{I} \frac{e^{t}}{II} d t}

\mathrm{\Rightarrow x \times e^{\tan ^{-1} y}=t e^{t}-\int e^{t} d t} \\

\mathrm{\Rightarrow x \times e^{\tan ^{-1} y}=\tan ^{-1} y e^{\tan ^{-1} y}-e^{\tan ^{-1} y}+c} \\

\mathrm{x=1, y=0 \Rightarrow 1\times e^{0}=0-e^{0}+c \Rightarrow c=2} \\

\mathrm{y=\tan 1 \Rightarrow x \times e^{1}=1 \times e^{1}-e^{1}+2 }\\ \Rightarrow \mathrm{x=2 / e}

Hence the correct answer is option 2

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manish painkra

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