223 
, . , . . dA . dA . 
e dai 'valori di A' — — u -4- v , ecc. 
du dv 
deduciamo 
dD _ dot cL4\ dD' vw , dA. 
dv dv~*~ U dv) ’ du JL. ' du a dui ’ 
dD dD 
dv 
- = 2 [“ ,s " v ~ sf) ~ 2a ’ (s ' 7 ~ sY) 1 
e posti 
(!) == rnF — nE , (2) = mG — nF , (1') = m'F — ri E, ([") = m" F—ri'E, ecc. 
essendo 
Ay = C D — ( I ) c' h- (2) c, AS 1 = B D' — {{') ò'-h (2') b , 
A f = BD" -(1 ") 6' -t- (2") 6, ecc. 
ne seguono 
A*(S''7— Sf) = (Cb — Bc) [D(2") - X)' , (2)]-(C(> , -Bc')[»(i") - D" (I )] 
n-(W-6' c )[(l")(2Hl)(2")] 
A J (S'7 - e-/') = (Cf> - Z)c)Fd(2') — D’(2)]- (C6'-Bc')[b(I')_D'(I)] 
+ 4[(!')(2)-(l)(S!')] ecc. 
A* 
M 
W~ 
-4- 
^') = 2 [C(2')-B'(2)] 2V(ÈV - Fa) 
[o(i")-fl"(t)]2“( Fa '- Ga ) ; 
