!J .'!.: I 



r of the line (1) traces during the 

 i adiua LP % paralK-1 to the jy-plane. The eqoa* 

 : liat path is 



Y . :: 



But in the ia-plane, before revolution U begun, LP is the 

 abscissa 2 of P \ hence, by equation (1), 



o that the equation <>f the path of P is 



(2) 



But P is any point of line (1); hence eqn ) is 



itfied by every point of the lints and represents tin- surface 

 generated by the line, \vhi.-li is tlu> required conical surface. 

 Tk* tpher* formed by revolving about the *-<ixi the 



+ f-26. . . (8) 



I n this case, any point P of the curve traces during the revo- 

 luti 'Una NP* parallel to the xy-plane. The 



equation of this path is therefore 



