\[ \left[2\frac{d^2y}{dx^2} + \left(\frac{dy}{dx}\right)^2 \right]^{\frac{3}{2}} = \frac{d^3y}{dx^3} \]
The degree of the differential equation
\[ \left[1 + \left(\frac{dy}{dx}\right)^2 \right]^{3/2} = \frac{d^2 y}{dx^2} \]
is ______.
Kepler's second law (law of areas) of planetary motion leads to law of conservation of