We have to prove that C1[0,1] is not complete with the norm:
∣∣f∣∣∞=supx∈[0,1]∣f(x)∣
The right sequence for norm is fn=x+x1
Notice that n∈N:fn∈C1[0,1]
let f=x
We see that fn converges to fin sup norm in C[0,1] , Thus it is cauchy.
C1[0,1] is a supspace of C[0,1] and all terms of (fn) are in C1[0,1] ,So
As the fn converges to C[0,1]
⟹(fn) is Cauchy in C1[0,1].
So Given space is not complete with norm ∣∣f(x)∣∣∞=supx∈[0,1]∣f(x)∣
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