218 ANALYTIC GEOMETRY [Cii. VIII. L82, 



; but represents a con focal hyrx-rbola when a a >^ a >6 ;2 ; given 



1>- :! mine the nature of the follow s and also their 



directrices, centers, semi-axes, and later* recut : 



19. y= 



20. jr'- 



21. x = 

 22. 



23. 



24. 9(*'-y)=3y(l+2z-3.y). 



25. Show that the polar equation of the parabola, with its vertex at the 



26. Show that if the left haml focus be taken as pole, the polar equation 

 of the ellipse is p = f< *"**)' 



1 CC080 



27. Derive the polar equation of an hyperbola, with ita pole at the 

 focus, eccentricity 2, and the distance of the focus from the dir 

 equal to 6. 



