Separable De
1. The problem gives the differential equation $$x y' = y + 2x^3 \sin^2\left(\frac{y}{x}\right).$$
2. We need to find the solution or explore this equation step by step.
3. First, let's rewrite the equation to isolate $y'$:
$$y' = \frac{y}{x} + 2x^2 \sin^2\left(\frac{y}{x}\right).$$
4. Introduce the substitution $v = \frac{y}{x}$, hence $y = vx$.
5. Then, $y' = v + x v'$ by the product rule.
6. Substitute into the original equation:
$$v + x v' = v + 2x^2 \sin^2(v).$$
7. Cancel $v$ on both sides:
$$x v' = 2x^2 \sin^2(v).$$
8. Divide both sides by $x$ (assuming $x \neq 0$):
$$v' = 2x \sin^2(v).$$
9. Express the differential equation as:
$$\frac{dv}{dx} = 2x \sin^2(v).$$
10. Rewrite as separable equation:
$$\frac{dv}{\sin^2(v)} = 2x \, dx.$$
11. Recall that $\frac{1}{\sin^2(v)} = \csc^2(v)$.
12. Integrate both sides:
$$\int \csc^2(v) \, dv = \int 2x \, dx.$$
13. The integral on the left is:
$$\int \csc^2(v) \, dv = -\cot(v) + C.$$
14. The integral on the right is:
$$\int 2x \, dx = x^{2} + C.$$
15. Equate the two integrals (absorbing constants into one $C$):
$$-\cot(v) = x^2 + C.$$
16. Substitute back $v = \frac{y}{x}$:
$$-\cot\left(\frac{y}{x}\right) = x^2 + C.$$
17. This implicit solution relates $x$ and $y$.
Final answer:
$$-\cot\left(\frac{y}{x}\right) = x^2 + C.$$