(i) Let p be a point of the compact interval I=[a,b]⊂R and let δp:C(I)→R be defined by δp(f)=f(p). Show that
δp:(C(I),∥⋅∥∞)→R
is a continuous, linear map but that
δp:(C(I),∥⋅∥1)→R
is not continuous.
(ii) Consider the space C(n)(I) of n-times continuously differentiable functions on the interval I. Write
∥f∥∞(n)=k=0∑n∥∥∥∥f(k)∥∥∥∥∞ and ∥f∥1(n)=r=0∑n∥∥∥∥f(k)∥∥∥∥1
for f∈C(n)(I). Show that (C(n)(I),∥′⋅∥∞(n)) is a complete normed space. Is the space (C(n)(I),∥⋅∥1(n)) also complete?
Let f:I→I be an n-times continuously differentiable map and define
μf:C(n)(I)→C(n)(I) by g↦g∘f.
Show that μf is a continuous linear map when C(n)(I) is equipped with the norm ∥⋅∥∞(n).