S_1 = (7.975217860764686, 1.8747007474383612)
A_{1} = (4.92, -0.84)
c = Circle(S_1, A_{1})
a = 0 (slider from 0 to 5, step 1)
p = Tangent(A_{1}, c)
A = Point(p)
f = OrthogonalLine(A, p)
d = Circle(A, Radius[c])
A' = Intersect(d, f, 2)
p' = OrthogonalLine(A', f)
h = LineBisector(S_1, A')
S_2 = Intersect(f, h)
k_2 = Circle(S_2, A)