-a/e

a/e

Với mọi điểm M thuộc elip, ta luôn có:

 \frac{ MF_1 }{d(M;Δ_1) } \; = \; \frac{ MF_2 }{d(M;Δ_2) } \; = \; e \; (e \; < \; 1)  

O = Intersect(yAxis, xAxis)
F_1 = Point(xAxis)
F_2 = Mirror(F_1, yAxis)
a = 15.7 (slider from 0 to 40, step 0.1)
c: x(F_2)
b: sqrt(a * a - c * c)
d: x * x / (a * a) + y * y / (b * b) = 1.0
e: c / a
Δ_1: x = -(a) / e
Δ_2: x = a / e
M = Point(d)
f = Segment(F_1, M)
g = OrthogonalLine(M, Δ_1)
A = Intersect(Δ_1, g)
h = Segment(M, A)
B = Intersect(Δ_1, xAxis)
C = Intersect(Δ_2, xAxis)