Related Formula
d((y)/(x)) = (x dy - y dx)/(x²)$$d\left(\frac{y}{x}\right) = \frac{x\,dy - y\,dx}{x^2}$$
Core Logic
Let us reorganize the given differential equation:
x ((y)/(x)) (dy)/(dx) - y ((y)/(x)) = x$$x \cos\left(\frac{y}{x}\right) \frac{dy}{dx} - y \cos\left(\frac{y}{x}\right) = x$$
((y)/(x)) [ x (dy)/(dx) - y ] = x$$\cos\left(\frac{y}{x}\right) \left[ x \frac{dy}{dx} - y \right] = x$$
Dividing both sides by x²$x^2$:
((y)/(x)) ( (x dy - y dx)/(x²) ) = (1)/(x)$$\cos\left(\frac{y}{x}\right) \left( \frac{x \, dy - y \, dx}{x^2} \right) = \frac{1}{x}$$
Step 1: Integration Process
Let (y)/(x) = t$\frac{y}{x} = t$. The equation transforms to:
t dt = (1)/(x) dx$$\cos t \, dt = \frac{1}{x} \, dx$$
Integrating both sides:
t = ln|x| + c ((y)/(x)) = ln|x| + c$$\sin t = \ln|x| + c \implies \sin\left(\frac{y}{x}\right) = \ln|x| + c$$
Step 2: Resolving Constant via Boundary Limits
Given boundary state y(1) = (π)/(3)$y(1) = \frac{\pi}{3}$:
((π/3)/(1)) = ln|1| + c √(3)2 = 0 + c c = √(3)2$$\sin\left(\frac{\pi/3}{1}\right) = \ln|1| + c \implies \frac{\sqrt{3}}{2} = 0 + c \implies c = \frac{\sqrt{3}}{2}$$
Comparing with the given form ((y)/(x)) = ₑ|x| + (α)/(2)$\sin\left(\frac{y}{x}\right) = \log_e|x| + \frac{\alpha}{2}$:
(α)/(2) = √(3)2 α = √(3)$$\frac{\alpha}{2} = \frac{\sqrt{3}}{2} \implies \alpha = \sqrt{3}$$
Therefore:
α² = 3$\alpha^2 = 3$
Pattern Recognition
Recognize the standard quotient derivative pattern early. Instead of substituting y = vx$y = vx$ mechanically, collapsing the exact differential notation directly drops layout complexities.
Chapter Mix
Class 12 Mathematics: Differential Equations