TltK 



[Art. 155 (a)] 



<k coe <fo = 0, 



refore o>, <fo 90, 



the eccentric angle* of the extremitie* of ttco conjugal* 

 diameter* differ by a right <i/ 



1561 EqnUonjugste diameters. If two conjugate diameters be equal 

 ", = CP s (see FU-- 11.'). then the properties given 

 in the preceding article lead to other simple ones. 



Let 4, 1^ the cccfMitric angle of /',. th-r, ^+90 is the eccentric angle 

 .; hence the coordinates of P l and P t are (a cos ^ 6 siu ^) and 

 (-o sin i.. ft cos d.), and since 



TW. A!. UKOM. 17 



