The Figure shows elliptical orbit of a planet m about the sun S. The shaded area SCD is twice the shaded area SAB. If t₁ is the time for the planet of move from C to D and t₂ is the time to move from A to B then:

t₁ = 2t ₂

Areal velocity of a particle moving in a planetary motion is constant.

Velocity for area SCD : A₁ / t₁ ; Velocity for area SAB : A₂ / t₂

\(\Rightarrow \frac{A_1}{t_1} = \frac{A_2}{t_2}\)

It is given that $ A_1 = 2A_2$

\(\Rightarrow t_1 = 2t_2\)