- #1
Adblax
- 7
- 0
Homework Statement
Fix a<b in R, and consider the two norms Norm(f)1:=Integralab( Modulus(f)) and Norm(f)Infinity:= sup{Mod(f(x)): a <= x <= b} on the vector space C[a,b]. This question shows that they are not equivalent.
a. Show that there is K in R such that for all f in C[a,b],
Norm(f)1 <= K*Norm(f)Infinity
b. Show that there is no K in R such that for all f in C[a,b],
Norm(f)infinity <= K*Norm(f)1
c. Consider the sequence of functions (fn) in C[-1,1] given by fn(x):=x1/(2n-1)
Is (fn) a cauchy sequence in (C[-1,1], Norm(f)1)? Why?
Is (fn) a cauchy sequence in (C[-1,1], Norm(f)Infinity)? Why?
Homework Equations
Cauchy Convergence Definition:
For all E>0, There exists M(E)>0, in the natural numbers, such that for all m>=n>=M(E), Norm(fm-fn)<E
The Attempt at a Solution
Found the first two parts relatively easy I think, for a taking k to be (b-a) and for b, considering the sequence of functions
fn(x):= { n2-nx for 0<=x<=1/n
0 otherwise
However, for the proof of cauchy sequences I am at a loss, as we cannot use normal convergence in the normed vector space as it converged to something that isn't continuous. So I am trying to use the definition of cauchy convergence, for the first part I have tried splitting up the integral into [0,1] and [-1,0] but have no idea for the second part.
Last edited: