( 227 ) 



Si antem aequilibrium adest inter vires agentes, 

 adfit ctiam acquilibrium inter vires diverforum 

 fystcmatum necesfe est. Habcmus igitur, e 

 Theoria virium parallciarum , fequentes aequiii- 

 brii conditiones : 



i^. In plano XO Y: 



l 1? cof. ci + ^F' cof. «' + J P" cof x" 

 + caet. — o Ci), 



§ P w/ /3 + J P cof /3' + f P" cof /8" 

 + caet. — o C^), 



J P (o 3; cq/: « ~ 2 X cof /3) + f P' (23»' cof »' 



— o,x' cof /3') + caet. = (3). 



2<>. In plano X O Z : 



IV cof cc ^r f P' cof a' + a P" cof a." 

 + caet. —o C'')» 



l? cof y + 1 P' cof 7' + l V" cof v" 

 + caet. — o C4) » 



IV^^^ixcof^-izcof^^-^W^ix' cof y ' 



— 22' cof. »') Ji. caet. — Q Cs)- 



3°. In plano Y O Z : 



IP ctf/. /S + f P' co/. /3' + I P" cV"- /3 



+ caet. — o • C^) •> 



i? cof y + l P' cof y' + I P" co/. y'' 



+ caet. rz o C4) » 



Ji?(i2zcof0-2ycof7^+ irQ^zcof^' 



— 2y' cofy'^ + caet. — o C6), 



Perfpicuum autem cst , has novcm aequationcs , 

 postquara per » divifae funt , rcduci ad fex ae- 



T 2 qua- 



'f 



