fiet cot.>]=^.^ = |^, cft enim in Triangulo FSE, 

 tang. »:zf|. Quum vero fir, Ui*|.|5 fict ^A F ^.BT 

 et pro BF adhibendo EF-EB, SE- s Jf = ^.BT, 

 hincque 



S E S_E E_B i S_ V BJT S_E EB i. 5V . CJ BJ 



C E ■~ r ~ E P " E C ~" ■"" TVCE E F ' E C ~' T V ' cl ' C B" 



Nunc vero habemus ob triangula CES, CBE, CFE, CTB 



rectangula : 



ll^cqt. <P 7 1?- cof - ' i ; 1 p = cot - » ; cl- fini ' cl= c0t - x ' 



tumque yti fupra \\ — &j[ ; confequimiir itaque 

 cotv4> 5E cot. ni cof. i rf- ^- Mfti-- 



§. 6. ' Quo huius formulae \ d\$ facilior in computo 

 adhiberi queat, ponamus cot. 4/ *e —^ 11 — , critque : 



cot. <$> = cot: yj' ( cot. \|^ fin. 'i -+- cof. i ) — cot. q "^- '"t^., 



quae -formula pro computo inflituendo valde eft concinna; 

 cacterum etiam Geometrice hae formnlac admodum ele- 

 ganter inueniuntur fequentem in modum. Ob triangula 

 CEF, CBT reclangula, fiet tang. C F B : tang, CTBzBT : BF, 

 eft vero 



B T : B F zf fin. B F T : fin. B T F .— cof. •>, • fin. , hinc 

 tang. C F B ( '±z tang. vjv ) : tang. X — cof. y\ : fin. 0. 

 Porro habetur tang. (p: tang. 'y\ — C E : F E ob triangula 

 FES, CES ad E rcctangula, eft vero in triahgtiio C E F 

 C E : F E ~ fm. C F.E : fia. E C F =± fin. vj, : f n. '( / ~h vp ) , 

 ob CEF~/,fiet igitur tang. <£): tang. vj — fin. vp :fin.^'-f vJA 



§. 7. Quoniam angulus vj/ , proiiti anguli X et , 

 fiue pofitine "fiue negatiue accipiantur, pofiiiuos et ncpati- 

 vos valoreK inducrc poteft, neccftum eft, vt breui cxplica- 

 tione perfpicuum rcddatur. r . quacnam formula quolibct iu 



cafu 





