Def 17.3

𝑓:(𝑥,𝑑)(𝑦,𝑑) is called Lipschitz
if 𝑑(𝑓(𝑥),𝑓(𝑦))𝑘𝑑(𝑥,𝑦)
where 𝑘>0 is called Lipschtz constant

Thm pg.143

if 𝑓:𝐴 is Lipschitz function, 𝑓 is uniformly continue in 𝐴

Thm 24.1

The best(smallest) Lipschitz constant equal to the first order derivative of a differentiable function.

OH 35.1

Thm D

for 𝑓 continue, 𝑓 bounded and 𝑓 integrable 𝑓 Lipschitz

Proof

by FT:

𝑓(𝑏)𝑓(𝑎)=𝑏𝑎𝑓(𝑡)𝑑𝑡Δsup𝑓(𝜉)(𝑏𝑎)sup𝑘𝑓(𝜉𝑘)

Thm E

𝑓 and 𝑓 is bounded 𝑓 is Lipschitz

Proof

by MVT

(𝜉(𝑎,𝑏))𝑓(𝑏)𝑓(𝑎)𝑏𝑎=𝑓(𝜉) 𝑓(𝑏)𝑓(𝑎)=𝑓(𝜉)(𝑏𝑎)(𝑏𝑎)sup𝑓

Thm

𝑓 uniformly continue 𝑓 Lipschitz