===== »7i = 



§. 17. Aeqnationes (§. 15. i'»,) univeifaliter pro 

 omnibiis Trian^iilis ortJiogonalibiis demonftrata , fi iam in 

 Triangulo UEF ad E rea.ingulo adhibcantur, nanciscimur 

 (J. 13.) tangFfinEF^tan^EU, h. e. 



tang F cof a — cot B , 



qu{\ aequatione lefolvuntur cafus II. 3. a. III. n. (§. ic). 



|. 18. In eodem Triangulo eft (J. 15.) fin F fin F G 

 — fin E , h. c. 



finFcof^zzcofB , 



imde folvuntur cafus II. i. a. 11. :. a. III. ^. (J. ic.); at- 

 que his fex aeqiiationibus omnia Trigonomeliiac fphacricae 

 leclangiilac prublemata icfoluta funL. 



$. 19. Propofito iam Triangulo f])hacrico non reflan- 

 Tig. 13. gnlo AliC, cuiiis anguli funt A, B, C, lat( ra BC^or, ACrp, 

 AB ry, priora a ct (3 producantur. donec fucrit CE CUrpo', 

 ideoque C polus circuli E D , cui arcus B A produflns oc- 

 currat in F: ficquc oricntur Triangula BEF, ADF, ad 

 E, D, reaangul.i, ubi BErrp-Z-a, AD— 5;."-(?, EDrC, 

 IJAF — A, EBFmso'-B. 



§. 20. In his Tiiangulis, pcr propriclalcs rcQangulo- 

 rum modo deinonftratas, habcmus ($. i s.) cofF- fmEBFcufEB, 

 ct cofF— finD AFcof A D, undc fcquitur 



fin B fin a — fin A fin f? , 

 qua aequationc rcfolvuntur cafus II. «. L. III. 2. r. (J. 11.). 



§.21. Ibidem cft (5.1-3.) 1g E F r tg E B F fin EBr 

 -tgBcof., tgDFiz:tgAcof|3, et (§. i-,.) t ^]}, F zz: J^. z=z 



