( 159 ) 



Si autem (p = i8o°, eric y^o^ five: 

 2 cof. (j V-H^ = o, 



ergo ~ V^ — H = 9o° — Ja-; undey — H = 5; 



quapropcer y ^ F (<p) =: 2 co/. | <|>, ec 



R = 2 P cfi/. I (p. 

 Unde fequitur : vim compofitam esfe diagona- 

 lem Rhombi , cujus latera vires aequales re- 

 praefentant (i). 



XXXVH. In opcre citato, quo haec demon- 

 flratio invenitur, alia data est demonftratio ana- 

 lytica ab Equite de Foncenex, absque 

 calculi difFerentialis et integralis ope ; ea au- 

 tem , utpote minoris momenti , omisfa , expo- 

 fituri fiimus demonftrationem P o j s fo n i i. 



XXXVIII. Agant vires aequales P in direc- 

 tionibus ^otP et ^P, angulum aVb = 2 (J) , 

 comprehcndentibus , crit ut fupra : 



R - P.F(2C?)), Hvc R = P.F(<?5). 

 Refolvantur vires P fingulae in duas vires ae- 

 quales Q, in directionibus ^'P, AP, ^'P, 

 B P agentes , eric ob easdem rationes : 



P 



(i) D^Alembertius hanc demonftrntionera pri- 

 imnn praebuit in fuo celebrato traccacu Dynamices 

 {Ttaifi cle Dytiarnique ;) cam auteiii dcrumfimus e Tom. II. 

 iVfiscell. Tiiiir. pag. 298 ; quo loco tradita csc et cmcU' 

 data ab Eqiiite deFoucenex. 



