n21

n21 = 1.3 (slider from 0 to Distance[D, E] / Distance[Y, E], step 0.01)
C = Intersect(xAxis, yAxis)
B = Point(Ray[C, Vector[(-1, 0)]])
d = OrthogonalLine(B, xAxis)
ControlE = Point(Ray[C, Vector[(0, -1)]])
A = Point(Ray[C, Vector[(0, 1)]])
j = Line(A, B)
f = Line(ControlE, xAxis)
Y = Intersect(d, f)
D = Intersect(f, j)
b_1 = Segment(D, ControlE)
r: b_1 / n21
k = OrthogonalLine(D, f)
a = Segment(B, A)
b = Segment(D, B)
p_1 = Segment(C, A)
n_1 = Segment(C, ControlE)
E = Intersect(f, yAxis)
c = Circle(E, r)
H = Intersect(c, f, 1)
g = Line(B, H)
M = Intersect(k, g)
R = Intersect(g, yAxis)
h = Segment(B, M)
i = Segment(B, R)
l = Segment(R, C)
lugar1 = Locus(M, B)
m = Line(M, xAxis)
F = Intersect(m, yAxis)
n = Segment(F, C)
p = Segment(H, E)
q = Segment(H, M)
CasillaDeEntrada1 = Textfield(n21)
s = Segment(D, M)
e = Segment(B, Y)
DY = Distance(D, Y)
HY = Distance(H, Y)
t = Segment(C, Intersect[k, xAxis] - (1, 0))