I l-Il.
EXCERPTA MaTHEMATICA.
3M
ficie concavâ vitri cujus vertex in C, vt videantur veniile ex pundo A.
F A D c B
Ponatur nunc AE^oa— j, &.BE ^ b — cy. Cadit F
inter B & C ; & tune, pro certo, radij omnes ab A ve-
5 nientes divaricantur in vitro, | tanquam fi veniffent
ex B ; vel contra radij ab B venienies in vitro, cogun-
tur in aère tanquam û venifient ex A.
AC^a, AE ^ a — y,
BC^b, BE^ b + cy,
10 nç -,^ <^rr —rr + a^r + ■^^cy
id — tb >
— C' \ — 4bà — 4aa j — 4a* ) + Saa^j*
+ 2CC r' - 4'îfc / 3 + ^bb ( — 4abcc ^yy
) -i- 4bc i-' -: 4Jjc-cl-^'^ — Sdfrc ;
DE- V •
4a
— 4bbcc
— Sabby + Haabcy
— 8a **<:>•
4<ja — a ab -- 4bb
Nunc quceratur pundum F quod fit centrum cir-
culi tangentLs curvam in pundo E, & fiât : FC »> f,
