Číslo kroku

S_1 = (7, -6.9)
T = (14.48, -4.02)
k_1 = Circle(S_1, T)
f = Line(S_1, T)
S_2 = Point(f)
k_2 = Circle(S_2, T)
a = 0 (slider from 0 to 2, step 1)
p = OrthogonalLine(T, f)
S = Point(f)
k = Circle(S, T)