[ 6 1 
denote any quantities exprefTed in terms of AC^ 
cD\ and D'd^ (independent of C c) and R\ 
T', as many other quantities affected in the 
very fame manner with ^ J G', and G' g ; and 
let R\ S", r, and R'\ S'\ be quan- 
tities, ftill, expreffed in the fame manner, in terms 
oi A Hy h Ty I iy and AKyk L\ L'ly refped:ively : 
’tis propofed to find an equation cxpreffing the 
relation of the indeterminate perpendiculars D'dy 
G'gy I'iy Idly fo that the q ^antity 
may be a Maximum or Minimum, at the fame 
time that the values of the other quantities R + 
+ R!' + K\ S+ S' +6" + S"'y and T+ F + 
(Jit or continue invariable. 
PutZ)V = a, G'g = /3, Tt—yy L7=cT'j and 
let the fluxion of (fuppofing a variable) be de- 
noted by q oty that of i?, by ra, ^c. ^c, then, fince 
(by the nature of the propofition) the fluxion of 
I 
