The pantograph
Author: Chris Sangwin
Date: 27 December 2006

Perhaps the most famous linkage is the pantograph.  This is used to enlarge and reduce drawings.  One form is shown below.  Move the point C, and watch the resulting point A.  Note that B is assumed to be fixed to the table.

B = Intersect(xAxis, yAxis)
C = (4.455555555555556, 1.614814814814815)
a = 3
c = Circle(B, a)
b = 3
d = Circle(C, b)
F = Intersect(c, d, 1)
G = Intersect(c, d, 2)
e = Segment(F, C)
f = Segment(C, G)
g = Ray(F, B)
h = Ray(G, B)
i = 1
k = Circle(B, i)
D = Intersect(k, h, 2)
E = Intersect(k, g, 2)
j = 1
p = Circle(D, j)
l = 1
q = Circle(E, l)
A = Intersect(p, q, 1)
m = Segment(D, G)
n = Segment(F, E)
r = Segment(E, A)
s = Segment(A, D)
t = Ray(A, D)
a_1 = Ray(C, F)
H = Intersect(t, a_1)
b_1 = Segment(H, D)
c_1 = Segment(H, F)