i6o	Elementa
lorum menfura , eft dimidium producum ex lingulis bafibus in ipfam bafium diftantiam, ac proinde fu perficies, pyramidis, truncata: sequatur dimidio produHo ex fummaperimetri bafis & lectionis. in diftantiam perpendicularem bafium...
COR. III. Si conus reftus plano bafi parallelo truncatus ponatur,, coni hujus, truncati verfus. bafim fuperficies. .aequalis eft dimidia produ&o ex peripheriarum fumma in coni truncati longitudinem five latus . Res autem aliter obtinetur, fi inveniatur circu* lus DE ( Fig. 30.) cujus peripheria aequalis fit femifummas peripheriarum BC, GM, Sumatur nempe. punftum D medium, inter B, G, ducatuique re&a DE parallela fe-dioni BG, hsec erit diameter circuli quadi-ti . Etenim duftis perpendicularibus Bfa, Dh, erit ob triangulorum DBf, DGh fimi-litudinem Bf: Df H Dh : Gh , ac proinde ob Bf Z1 Dh , erit etiam Df Z1 Gh; quare eadem eft differentia inter diametros BC& DE,, quae eft inter diametros,DE, GM; illa nempe differentia eft dupla re&as, Df yel Gh „ ideoque re£ta DE eft media proportionalis arithmetica inter BC, GM , feu quod idem eft ,. .diameter DE aqualis eft femifummas diametrorum BG, GM. Sed circuli utpote fi gurcfim il.es ^uas habent perk pherias. diametris, proportionales .( Schohcap* 3* Ergo- circumterentia circuli diametro DE defcripti , eft media proportionalis, arithmetica inter circumferentias diametris BC, GM defcriptas . Habebitur ergo coni truncati BCGM fuperficies.^ fi multiplicetur circuli