State Kepler's laws on planetary motion. Explain the way the three laws can be proved.

Explanation

1st part:
2nd part: If `r_1 and r_2` are the shortest and the longest distances of the planet from the sun , then the semimajor axis is given by `((r_1+r_2)/2)`.
1st law is proved from angular momentum conservation in a circular path.
Since, L= `2mxx` are velocity , for equal time, area swept will be same . so, 2nd law is proved.
From `F=(GM_0m)/(r^2),(mv^2)/r=F and T=(2pir)/(v)` one can prove `T^2prop r^3`. so, 3rd law is also proved.