Mathematics › Differential Equations › Homogeneous DE
A curve passes through the point $\left(1, \frac{\pi}{6}\right)$. Let the slope of the curve at each point…
A curve passes through the point $\left(1, \frac{\pi}{6}\right)$. Let the slope of the curve at each point $(x, y)$ be given by $\frac{y}{x}+\sec \left(\frac{y}{x}\right), x>0$, then the equation of the curve is
$\sin \left(\frac{y}{x}\right)=\log x+\frac{1}{2}$ $\operatorname{cosec}\left(\frac{y}{x}\right)=\log e+2$ $\cos \left(\frac{2 y}{x}\right)=\log x+\frac{1}{2}$ $\sec \left(\frac{2 y}{x}\right)=\log x+2$
Solution
Here $\frac{\mathrm{dy}}{\mathrm{dx}}=\frac{\mathrm{y}}{\mathrm{x}}+\sec \left(\frac{\mathrm{y}}{\mathrm{x}}\right)$
Let $\frac{y}{x}=v \Rightarrow y=v x \Rightarrow \frac{d y}{d x}=v+x \cdot \frac{d v}{d x}$
$\begin{aligned} & \Rightarrow v+x \cdot \frac{d v}{d x}=v+\sec v \\ & \Rightarrow x \cdot \frac{d v}{d x}=\operatorname{secv} \\ & \Rightarrow \int \cos v \cdot d v=\int \frac{d x}{x} \\ & \Rightarrow \operatorname{sinv}=\log _e x+C\end{aligned}$
$\Rightarrow \sin \left(\frac{y}{x}\right)=\log _e x+C$
Putting $\mathrm{x}=1, \mathrm{y}=\frac{\pi}{6} \Rightarrow \mathrm{c}=\frac{1}{2}$
$\Rightarrow \sin \left(\frac{y}{x}\right)=\log _e^x+\frac{1}{2}$
Asked in: MHT CET 2022 (05 Aug Shift 1)
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