Curve Stitching a Parabola
Author: cwl

Curve stitching.  Drag points A and C.  
Can you prove that the strings form the
set of tangents to a parabola?  

A = (4.837000000000001, 4.809000000000001)
B = (4.86, -2.88)
a = Line(A, B)
C = (11.976000000000003, -1.7491999999999994)
b = Line(B, C)
D = Midpoint(A, B)
E = Midpoint(B, D)
F = Midpoint(D, A)
G = Midpoint(A, F)
H = Midpoint(F, D)
I = Midpoint(D, E)
J = Midpoint(E, B)
K = Midpoint(B, J)
L = Midpoint(J, E)
M = Midpoint(E, I)
N = Midpoint(I, D)
O = Midpoint(D, H)
P = Midpoint(H, F)
Q = Midpoint(F, G)
R = Midpoint(G, A)
S = Midpoint(B, C)
T = Midpoint(C, S)
U = Midpoint(S, B)
V = Midpoint(B, U)
W = Midpoint(U, S)
Z = Midpoint(S, T)
A_1 = Midpoint(T, C)
B_1 = Midpoint(C, A_1)
C_1 = Midpoint(A_1, T)
D_1 = Midpoint(T, Z)
E_1 = Midpoint(Z, S)
F_1 = Midpoint(S, W)
G_1 = Midpoint(W, U)
H_1 = Midpoint(U, V)
I_1 = Midpoint(V, B)
c = Line(A, I_1)
d = Line(V, R)
e = Line(G, H_1)
f = Line(U, Q)
g = Line(F, G_1)
h = Line(W, P)
i = Line(H, F_1)
j = Line(S, O)
k = Line(D, E_1)
l = Line(Z, N)
m = Line(I, D_1)
n = Line(T, M)
p = Line(E, C_1)
q = Line(A_1, L)
r = Line(J, B_1)
s = Line(C, K)