Acc.  To kelper's law,  the sun is at one of the focus of the planet's path.  It's an ellipse having two focus and two directrix.  Do all the paths of planet,  have different foci and directrix or have common focus and directrix? 

As far as I understand it, the orbit of a planet will always have the same focus and directrix, with the caveat that the entire ellipse may in fact rotate about the focus due to GR effects.

On 17/10/2018 at 2:43 AM, muskan said:

Acc.  To kelper's law,  the sun is at one of the focus of the planet's path.  It's an ellipse having two focus and two directrix.  Do all the paths of planet,  have different foci and directrix or have common focus and directrix? 

The planets all have the Sun at one focus. They all have different directrices because they are not aligned in the same way (and are not even in the same plane). [Assuming I know what a directrix is!]