86 

 and 



k ,a = 



If 



then 



Mr Greenhill, On Conjugate Functions 



W AB.CD 



(m - ni') 2 +{n+ n'f ~ AC 2 



x -\-iy = z, x — iy = z ; 

 % + in = u, %—ir) = u'; 



r 2 = z — a . z — b, 



r 2 = z—b . z — a, 



r, 

 r 



[Mar. 21, 



2 = z - c . z - d, 

 = z — d. z — c; 



and we may put 



z — b a - c 

 and therefore, changing i into — i, 



= sn u, 

 = en 2 u, 

 = dn 2 u ; 



