State Keplers' laws of planetary motion.

Explanation

Kepler stated the following three laws to explain the motion of the planets

(i) Law of orbit: Every planet moves around the sun in an elliptical orbit with sun at one of its foci.
(ii) Law of areas: The line joining the sun and planet sweeps out equal areas in equal intervals of time is known as areal velocity. A planet takes the same time to travel from A to B as takes from C to D.
(iii) Law of period: The square of time for the planet to complete a revolution about the sun is proportional to the cube of semimajor axis of the elliptical orbit.
i.e., `T^(2) prop R^(3) or (T^(2))/(R^(3))` = constant
Here, S= forcus of ellipse R= semimajor axis of ellipse.