
d(v, z)≤d(v, w) + d(w, z)v, w, z ∈V
d(v, z)≥ |d(v, w)−d(w, z)|v, w, z ∈V
R3
hx, yi=x1y1+x2y2+x2y3+x3y2+ 2x3y3
hx, yi=x1y1+x2y2−3x2y3+x3y2+x3y3
hx, yi=x1y1+x2y2+x2
3y2
n a1, . . . , an∈R
h−,−i :Rn×Rn−→ R
(x, y)7−→
n
X
i=1
aixiyi
V=C0([a, b],R) [a, b]
Rα > 0
Φ : V×V−→ R
(f, g)7−→ α·Zb
a
f(x)g(x)dx
A An
n≥1
Vh−,−i T:V−→ V
V×V−→ R,(v, w)7−→ hT v, T wi
V f, g ∈V
Zb
a
f(x)g(x)dx
≤Zb
a
f(x)2dx1/2
·Zb
a
g(x)2dx1/2