State Kepler's laws of planetary motion.

Explanation

(1) Kepler's first law or the law of orbits (Feb. 18) : The orbit of a planet about the sun is an ellipse, with the Sun at one focus of the ellipse.
(2) Kepler's second law or the law of area (Feb. 18) : The straight line joining a planet the Sun sweeps out equal areas in space in equal intervals of time.
(3) Kepler's third law or the law of periods or the harmonic law : The cube of the semimajor axis of a planet's orbit is directly proportional to the square of the planet's period of revolution.