x, x0∈E
∀y∈A, kx−yk≤kx−x0k+kx0−yk
d(x, A)≤ kx−x0k+kx0−ykd(x, A)− kx−x0k ≤ kx0−yk
d(x, A)− kx−x0k ≤ d(x0, A)
d(x, A)−d(x0, A)≤ kx−x0k
|d(x, A)−d(x0, A)|≤kx−x0k
x7→ d(x, A)
x7→ d(x, CEU)K
α= minx∈Kd(x, CEU)x0∈K
α= 0 x0∈ CEUCEU x0/∈U x0∈K
α > 0
∀x∈K, B(x, α)⊂U
f x 6=y
kf(x)−f(y)k<kx−yk
f(x) = x f(y) = y
δ:x7→ kf(x)−xkK
δ K
c∈K
∀x∈K, δ(x)≥δ(c)
f(c)6=c
δ(f(c)) = kf(f(c)) −f(c)k<kf(c)−ck=δ(c)
c f(c) = c
x6=y
d(x, y) = d(f(x), f(y)< d(x, y)
g:x7→ d(x, f(x)) K
g K g
x0∈K
f(x0)6=x0
g(f(x0)) = d(f(f(x0)), f(x0)) < d(f(x0), x0) = g(x0)
x0f(x0) = x0
α, β I
a, b ∈Rα, β
f([a;b]) = [α;β]f[a;b]
A={x∈[a;b]|f(x) = α}B={x∈[a;b]|f(x) = β}
∆ = {|y−x| | x∈A, y ∈B}
∆R
m
(xn)∈AN(yn)∈BN
|yn−xn| → m
A(xn)
(xϕ(n))A(yϕ(n))
B x∞y∞
x∞∈A, y∞∈B|y∞−x∞|= min ∆
I[a;b]
x∞≤y∞J= [x∞;y∞]