[ 345 ] 
9> Let a a, Pp , be any two firft diameters; b b, qj, their fecond diameters, 
Plate xiv. Fig. 4. 
Draw the ordinates pd, qj:, to the diameter A a, and the ordinate pi, to the dia- 
meter b b. 
Let pt be a tangent, and pm be perpendicular, to the curve, in P; FT cutting Ai(, 
B b, produced, in T, t ; and pm, in M, m. 
Put the fubtangent dt =r, dt zn a-. 
Let AT = r, pm — t, ce iv, ct — q — x ± s zz t ± r. 
Put s, s', — fine and cofine of the angle mpd, or angle P/wB. 
R tabular radius. 
12. Confequently 
p d l _ xx 
XX 
tt AC 
b d i zh.cc -t-y y 
CC B C 
LvrrilyyrtADtfrtCDT, 
cc 
T4. Therefore ae a=(~ x ADa =~ xix~) xxzzcd 
'dt 1 ss 
■2 
In 
