{c — c' ) fui. a fin. bfin.c — lix. (fin. 2 ^-fni. 2^-2 cof. c fin.(^-«) ) 



4- ^ j/ (fm.2 ^-f-fin. 2 fl— 2 cof. ^ fm.(a-f ^) ), 

 vnde ob 



fm. 2 ^ — fm. 2 a zn 2 cof (b -\- a) fm. {b — a) ct 

 fin. 2 b -\- fiti. 2 a — 2 fin. (Z» -I- fl) cof (^ — a) , 

 colligitur ,^^^ ^^ ^,. .{ifhir:). 



(f — (r')fiii.fffm.^fln.fzr^jjLfin. (^ — a)(cof (^ + fl) — cof^) 



-|-:>'fin.(Z»-+fl)(cof (^-fl)-cof (;) 

 ~fj(. fin. (fli — Z^^fin. jfin. (j — £■) 

 < -f vfin. (a + ^) fin.( J — fl)fin. (j-- ^) 



exiftente s Tizl (a ~{- b -+- c). Haec igitur formula infer- 

 viet pro inueniendo valore ipfius c ~ c', quoties corredliun- 

 culas ex {a — a')% {b~b'Y et {a — a') {b — b') oriundas 

 ncgligere liceat. 



§, 10. Ex aequatione fupra inuenta : 

 (cof c cof a cof b) fin. a^ fin. b' — (cof t' - cof «' cof b') fin.a fin.^, 

 habetnr 



( cof c - cof a cof b ) fJIL^-X - cof f' - cof a' cof b'y 

 inde vero colligitur 

 cof c' — cof ( fl' — Z»' ) z cof c' — cof c' cof b' — fin. a' fin. b' 



cof.(.'-i')-cof..'= = fin.(.-«)an.(J-*)'i:0;|-', 

 fiinili ratione inueniemus 

 * cof f'-cof («' + //') = (cofr-cof(« + ^))^';i^--^ vel 

 cof. c' - Qoi\{a' + ^') — 2 fin. s fin. ( j - c) flJh^-'^ , 

 quie formulae itcrum inferuire poterunt ad determinandum 

 cof f'. Prima harum formulanirr. nimiri.'n: 



cof {a' -b')- cof c' — ( col. {a-b)- cof c)^^--^^ , 



Vj^ «i .nS vfus 



