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AP EAMCET · Maths · Differential Equations

The general solution of the differential equation \(\left(x \sin \frac{y}{x}\right) d y=\left(y \sin \frac{y}{x}-x\right) d x\) is

  1. A \(\cos \left(\frac{y}{x}\right)=\log |x|+c\)
  2. B \(\cos \left(\frac{y}{x}\right)=\frac{1}{x}+c\)
  3. C \(\cos \left(\frac{x}{y}\right)=\log |y|+c\)
  4. D \(\cos \frac{\mathrm{y}}{\mathrm{x}}=\frac{2}{\mathrm{x}}+\mathrm{c}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\cos \left(\frac{y}{x}\right)=\log |x|+c\)

Step-by-step Solution

Detailed explanation

\(\frac{dy}{dx} = \frac{y \sin \frac{y}{x} - x}{x \sin \frac{y}{x}} = \frac{y}{x} - \frac{1}{\sin \frac{y}{x}}\) Let \(y=vx \Rightarrow \frac{dy}{dx}=v+x\frac{dv}{dx}\). \(v+x\frac{dv}{dx} = v - \frac{1}{\sin v}\) \(x\frac{dv}{dx} = -\frac{1}{\sin v}\)…