PHYSICAL AND LITERARY. 117 
to each other, meeting the curve in C, 
D; jet CE, a tangent to the curve at C, 
meet BD in E; join AD, AE, BC, and 
Jet AE meet the curve in F: The tri- 
angle ABC will be greater than the | 
fector ACF, but lefs than the fector 
ACD. 
Jorn CD. Becaufe AC, BE, are paral- 
, Jel, the triangles ABC, AEG, will be equal: 
But the triangle AEC is greater than 
the fector ACF ; therefore the triangle 
ABC is greater than the fector ACF. A- 
gain, becaufe AC, BD, are parallel, the 
triangles ABC, ADC, are equal: But the 
triangle ADC is lefs than the feGtor ACD; 
therefore the triangle ABC is lefs than the 
_ fector ACD. 
PROP. IL. Fig.2. 
Let there be a curve AEB, wholly con- 
cave towards the ftreight line AB, and 
let C,D, be two points in the line AB; 
draw DE to any point E in the curve, 
and 
