Find the particular solution of the differential equation $(1 + y^2) + (x - e^{\tan^{-1} y}) \frac{dy}{dx} = 0$, given that $y = 0$ when $x = 1$.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $x =\frac{1}{2}\left( e^{\tan^{-1} y} + e^{-\tan^{-1} y}\right)$ ##
Given differential equation can be written as
$\frac{dx}{dy} + \frac{x}{1 + y^2} = \frac{e^{\tan^{-1} y}}{1 + y^2}$
$I.F. = e^{\int \frac{1}{1 + y^2} dy} = e^{\tan^{-1} y}$
Solution is given by
$xe^{\tan^{-1}y} = \int \frac{e^{\tan^{-1}y}}{1 + y^2} \times e^{\tan^{-1}y} dy + c$
$= \int \frac{e^{2\tan^{-1}y}}{1 + y^2} dy + c$
or $xe^{\tan^{-1}y} = \frac{e^{2\tan^{-1}y}}{2} + c$
when $x = 1, y = 0$ or $c = \frac{1}{2}$
$∴$ Solution is given by $xe^{\tan^{-1}y} = \frac{1}{2} e^{2\tan^{-1}y} + \frac{1}{2}$
or $x = \frac{1}{2} (e^{\tan^{-1}y} + e^{-\tan^{-1}y})$