X(9)    MITTENPUNKT

The Mittenpunkt, labeled 9, is 
X(6)-of-the-excentral-triangle, A'B'C'. 

Sketch contributed by Michael Stairs, 
January 2018.

Drag A, B, C.

2'

9

A = (0.32660380964808466, 4.553441017936882)
B = (-0.29929821444838106, 1.9397715209755506)
C = (1.9681063826350635, 1.9928102250008946)
f = Segment(B, A)
g = Segment(A, C)
h = Segment(C, B)
i = AngularBisector(B, C, A)
j = AngularBisector(C, B, A)
C'_1 = Midpoint(f)
B'_1 = Midpoint(g)
A'_1 = Midpoint(h)
m = OrthogonalLine(A'_1, h)
D_1 = Point(m)
k = OrthogonalLine(A, h)
l = OrthogonalLine(C, f)
n = OrthogonalLine(B, g)
p = LineBisector(h)
q = LineBisector(g)
r = LineBisector(f)
b = AngularBisector(B, A, C)
c = AngularBisector(A, B, C)
d = AngularBisector(A, C, B)
D = Intersect(d, f)
E = Intersect(c, g)
F = Intersect(b, h)
s = AngularBisector(B, A, C)
t = AngularBisector(A, B, C)
a = AngularBisector(A, C, B)
e = Line(A, C)
f_1 = Line(C, B)
g_1 = Line(B, A)
G = Point(e)
H = Point(g_1)
I = Point(f_1)
h_1 = AngularBisector(I, B, A)
i_1 = AngularBisector(H, A, C)
j_1 = AngularBisector(G, C, B)
C' = Intersect(h_1, i_1)
B' = Intersect(i_1, j_1)
A' = Intersect(h_1, j_1)
k_1 = Segment(C', B')
l_1 = Segment(B', A')
m_1 = Segment(A', C')
n_1 = OrthogonalLine(A', h)
p_1 = OrthogonalLine(B', g)
q_1 = OrthogonalLine(C', f)
C'_2 = Intersect(g_1, q_1)
B'_2 = Intersect(e, p_1)
A'_2 = Intersect(f_1, n_1)
c_1 = Circle(A', A'_2)
d_1 = Circle(B', B'_2)
e_1 = Circle(C', C'_2)
G' = Centroid(C', A', B')
r_1 = AngularBisector(C', B', A')
s_1 = AngularBisector(A', C', B')
t_1 = AngularBisector(B', A', C')
a_1 = Line(A', G')
b_1 = Line(B', G')
f_2 = Line(C', G')
g_2 = Mirror(b_1, r_1)
h_2 = Mirror(a_1, t_1)
i_2 = Mirror(f_2, s_1)
J = Intersect(g_2, h_2)
j_2 = Segment(C', J)
k_2 = Segment(B', J)
l_2 = Segment(A', J)

Tool: Centroid
Input: A, B, C
Output: G

D = Midpoint(A, B)
E = Midpoint(B, C)
s = Segment(C, D)
t = Segment(A, E)
G = Intersect(s, t)

Tool: Incenter
Input: A, B, C
Output: I

s = AngularBisector(B, A, C)
t = AngularBisector(A, B, C)
I = Intersect(s, t)

Tool: Incircle
Input: A, B, C
Output: c_1

g = Segment(A, C)
s = AngularBisector(B, A, C)
t = AngularBisector(A, B, C)
I = Intersect(s, t)
e = OrthogonalLine(I, g)
G = Intersect(e, g)
c_1 = Circle(I, G)