874 



L ('M. IV. 



i The traces on the planes :r = a, sc a,y6, y 

 are in each case a pair of int.'rso-tin^ str;>i^nt lines. 



Fio. 158 



(4) The equation may be written 



(1) 



or 



1. 



(2) 



a 2 



From equation (1) it appears that the trace on tin- 

 ry-plaiuj is the smallest of the system of ellipses parallel 

 to that plane, and that the sections increase continuously 

 and indefinitely as z increases from to oo. 



1'rom equation (2) it appears that the transverse axis 

 of the hyperbolas parallel to the yz-plane is parallel t<> the 

 y-axls. Similarly, for the as-sections the transverse axis 

 is parallel to the 2>axis. 



