) 17 ( IP?- 



f ag. Eodem modo etiam computcmus quanti- 

 tatem arcus O P ex formula 



cof. O P =j^, vt fequitur 

 a /. cof. a = 9,^989700 ad /. O P = 5,05"7(Joi4. 



fubtr. /. Cn. p — 9,7<592i87 adde 4)68557+9 



/. cof O P = 9,92975 1 3 9,7+3 1763 



ergoOPi= Si'*. 43'. 3'' ArcusOPzro,5535749-»* 

 fiueO P = 1 141 83 fec. 



§. 29. Confideremus nunc pari modo pentagonum Tab. 1. 

 regulare planum , feu potius tantum eius partem quintam , '^" 

 vni lateri refpondentem a b ^ cuius latus fit ab , cen- 

 trum circuli circumfcripti 0, eiusque radius a ■, qui, quia 

 tanquam incognitus fpedari debet, ponatur a — z^ ac 

 demiffo ex in latus ab perpendiculo op, ob angulum 

 aop— 3<5 gr. erit ap — z fin. 36 gr. et op — 2 cof 3<^gr« 

 ideoque flpin 0,5877853.2 et op = 0,8090170. zj area 

 vero trianguli aop erit ~ 0,2377(571. zs 



§. 30. Qiiia autem in hac figura angulus a p 

 eft tantum 54 gr. dum in fphaera erat 60 gr. , eo angulus 

 fphaericus neutiquam obtegi poterit, fed nimis paruus efl; 

 6 gradibus. Ad hunc ergo dcfedum fupplendum lateri ab 

 adiurgatur fegmentum circulare ai^b^ cuius arcus cum chorda 

 faciat angulum p a 'n — 6 o^t. vt fiat anguhis a t: — 60 z,r. 

 angulo fciiicet O A P obtcgendo aptus. Huius arcus cen- 

 trum fit in 1;, duftaque recla -y « — ^y tt, ob angulum 

 v a Tt — 90, erit angulus a v 1: — 6 gr.; quare fi ponamus 

 V a =1 «y, erit ^ =: fin. 6 gr. ideoque 



<y — ° P »f in. 36 gr. 



Jiii. 6gr. jin. 6 gr. 



Jiia Acad. Imp. Sc. Tom. IL P. L Q vndc 



