7* 



H I S T O I R E 

 af (|E") 4- o? |£) 4- A y II' -|- B' !T = o, 



*''&-) ■+- a// (W) +A // n / .+ B'n = D l 



3> 



a / (aj?_") + ,*" (_y£) -+. A' II" 4- B /7 ^ = 



a " (£_) + a /7 (^) ■+- A" n" + B // n / =o < • 



Ces equations combinees deux a deux, comme dans le J. 

 30. donnent apres les redu&ions, d U _ (a d x ■+■ b d y) II, 



a ir — (a 5 x 4- b a j) n' =_ (a (i) ?x + b (I) a r ) n, 



d II"— (a 5 x 4- 6 9 j) II" = (a (2) 5x4- b (2) 3/) n^, 

 d'ou Ton tire en integrant, 



jj/ __ e /(c 3 x -+- &_9 _> /* e — /(a 3 x +- 6 3 7) ( a (Il ^ x 



II" = e/i a3 * + ia >' f e —J [adx + bdy] (d 2] dx 

 Qr aBoi + bayz: ^; 4 -^ , 



b (I) 5j)n, 

 __/)n', 



a (I) 5x4- b (I) 5/ 



(acjy-f-a^) 



( a -) ( a -) 



G + A^+B^ 



/93nx 



V^ 1/2 / 



/ 33TI \ 



4- C __— 4- D ^ 2 J 4- E v 



n 



(„__■■ 



n 



a (2) 5x4- b (2) dy = 



n n 



(5^ + a^O 



G+A. 



C v gx2 4- D - d —J 



^) 



n J 



(__) (_.'\ 



ir - ir 



V _^ ir* _. 'V / 



-+-E-_ — 



ir j 



ir n' 



Subftituant ces valeurs dans les formules integrales, on a 



n = _ 



/ 



A' 8 $''-+■ A"d$' ) 



.ir 



