See Section 13.15.6 for similarities in the plane.
The similarity command creates a command to rotate and
scale about a given line.
similarity takes three mandatory arguments and
one optional argument:
L, a line (the axis of the rotation).
r, a real number (the scaling ratio).
θ, a real number (the angle of rotation).
Optionally, G, a geometric object.
similarity(L,r,θ) returns a new command which
rotates about L through an angle of θ and scales about L
by a factor of r. If r is negative, the direction of rotation
is reversed.
similarity(L,r,θ,G) returns and draws the
transformation of G.