•*3^f ) +9 ( ^<- 



Dumcnis talium triangulorum eft =:«, erit 



angulus A O B — ^ ; 

 at fi area totius Polygoni flatuatnr zrS, quae fimul crit 

 menfura anguli propofiti, area iftius trianguli AOB erit 

 — -. lam ex O in latus AB ducatur normalis OP, 

 latAis AB bi(Gcans , critque APizisfl, ct 



angulus AO P z=-. 

 Vocetur iam angulus OAB — Cj), «ritqnc cx fphacricis 



fia, (P — 



cof. i a 



Quia igitur huic angulo ctiam aequalis cll angulus 

 OBA, fumma angulorum trianguli AOB erit — aCp-f-^, 

 mde ablatis duobus re<flis «obtinebitur area triaoguliAOB 



hincque area totius Polygoni 



quae ergo erit menfura anguli folidi regularis propofiti. 



Corollarium L 



$. 32. Si igitur angulus folidus -conftet cx tribus 

 anguljs planis aequalibus zna^ ob « — 3 , erit 

 ^ . £oi: 60" 



quo angulo inuento erit menfura anguli folidi 



^ — 6(^-^—6(^—\ 80°. 



Corollarium II. 



,§. 33. Si angulus folidus cx quatuor conflet an- 

 ^uKs pljnis intcr fe aeqi;alibus =3«, ob ;? rr: 4 quaeratur. 

 .4^?/' Acad. Imp, Sc, Totn. II P. IL G angu- 



