State Kepler's law of orbit and law of equal areas.
Ist law ( Law of orbit ) : The orbital path in the solar system is an ellipse with sun as one focus.
2nd law ( Law of equal area ) : The radius vector joining the centre of the planet to the centre of sun traces out equal area in equal intervals of time.
i.e.The area velocity of the planet is constant
All planet revolves around the sun in the elliptical orbit, the sun as one of its focus.
The line joining sun and planet sweeps the equal area in equal time interval i.e. Aerial velocity is constant.