Kružnice devíti bodů − prochází:

středy stran trojúhelníku

patami výšek trojúhelníku

středy úseček spojujících vrcholy s ortocentrem

Nazývá se též Feuerbachova −  dotýká se:

kružnice trojúhelníku vepsané

kružnic trojúhelníku připsaných

A = (4.24, 4.11)
B = (4.92, -2.73)
C = (10.3, 4.19)
S_b = Midpoint(A, C)
S_a = Midpoint(C, B)
S_c = Midpoint(A, B)
a = Segment(A, B)
b = Segment(B, C)
d = Segment(C, A)
e = OrthogonalLine(A, b)
f = OrthogonalLine(C, a)
g = OrthogonalLine(B, d)
P_b = Intersect(g, d)
P_a = Intersect(e, b)
P_c = Intersect(f, a)
c = Circle(S_b, S_c, S_a)
V = Intersect(e, f)
S_{VC} = Midpoint(V, C)
S_{VB} = Midpoint(V, B)
S_{VA} = Midpoint(A, V)
h, i = AngularBisector(a, d)
j, k = AngularBisector(d, b)
D = Intersect(i, k)
E = Intersect(h, k)
F = Intersect(i, j)
G = Intersect(h, j)
l = OrthogonalLine(G, d)
m = OrthogonalLine(F, b)
n = OrthogonalLine(E, a)
H = Intersect(n, a)
I = Intersect(m, b)
J = Intersect(l, d)
p = Segment(G, J)
r = Segment(H, E)
q = Segment(I, F)
s = OrthogonalLine(D, a)
K = Intersect(s, a)
t = Segment(K, D)
c_1 = Circle(D, K)
d_1 = Circle(G, J)
e_1 = Circle(F, I)
f_1 = Circle(E, H)
o = false
u = false
v = false
w = false
z = false