Answer: (1) Law of orbits, (2) law of areas, (3) law of periods.
- Law of orbits: every planet revolves around the sun in an elliptical orbit, with the sun at one of the foci.
- Law of areas: the line joining the planet to the sun sweeps equal areas in equal intervals of time, so a planet moves faster when it is nearer the sun and slower when it is farther.
- Law of periods: the square of the period of revolution is proportional to the cube of the mean distance from the sun, \(T^2 \propto r^3\).