46 INVESTIGATION of fome 
3 rs ; 
terms, = >- Thus, in the 
terms, — a? — 43 — &c. to ae 
heptagon A+ B—a= , A+B+a= ae and A+ B}— 
4 
33 _ 
a= —. In the enneagon A+ B—a—b= a M+B+a 
oS 4 and A3-+ B’—as— 33 = “ and fo on. But in 
the enneagon, A is the cofine of 20°, or the fine of 70°, B is the 
fine of 30° = S a is the fine of 10°, and 3 the fine of 50°. 
Wherefore the fine of 70° = fine of 10° + the fine of 50°; the 
{quare of the fine of 70° + fquare of the fine of 10° + fquare 
of the fine of sor = ; and the cube of the fine of 70° — © 
- eube of the fine of 10° — cube of the fine of 50° = ns viz. 
thrice the cube of half the radius. And fo on. 
r—Oc* = r#— 473 KOc+6r'xOc —4r x Oe + Oc’, - 
On = r—4rxOa+6rxOa —47XOa +02, 
eye eR OELET XO — at ROE OL 
FO) = ri+4r3 xX OF+ 67x OF +4rxO0 +00, 
70d = r+4anxOd+ 6x Od +47rxOd +07, 
Bur 
