[ 3o6 ] 
cxprefTed by the equation 
— 71" ^ — 71' X *y* = Oy and 
dt (rzrfw) will be r= —ZlJLxuv. 
If u and V be refpedlively put for fr and dp, their 
relation will be expreffed by the equation 
If — If if — If X ~ Oy and 
d t (= f w) will be = ~ff - x uv. 
10 . 
Suppofe y — to z, (that fs, v — z/) and that th-e 
points d and f coincide in e. In which cafe the 
tangent dt will be a 777aximuniy and = eg — ac. 
It appears then that the a7'0 ae — the arc eg is 
c g — a c. 
Confeqtiently, putting JL for the quadrantal arc ag, 
■we find that the arc ae is — 
2 
t E — b n \ 
the arc e g = ! 
There are, I am aware, fome other parts of the 
arc ag, whofe lengths may be affigned by means of 
the whole length (ag) with right lines; but to in- 
velligate fuch other parts is not to my prei'ent pur- 
pofe. 
1 1 . 
Taking m and 7i each = i ; that is, ac (~AC) 
rz 1 , and eg — 2 y let the arc ag be then ex- 
7 preffed 
