take M0 = MetrStruct(# 1,Empty^2-to-zero #); ( M0 is strict & M0 is ultra & M0 is Reflexive & M0 is symmetric & M0 is Discerning & M0 is triangle )
M0 is ultra
proof
let x,
y,
z be
Element of
M0;
METRIC_1:def 19 dist (x,z) <= max ((dist (x,y)),(dist (y,z)))
thus
dist (
x,
z)
<= max (
(dist (x,y)),
(dist (y,z)))
by Th25;
verum
end;
hence
( M0 is strict & M0 is ultra & M0 is Reflexive & M0 is symmetric & M0 is Discerning & M0 is triangle )
; verum