Solution

ID: past-exam-of-the-functional-analysis-i-course-of-the-university-of-oxford/2023/3/c/iii/solution

From , one is an eigenvalue. Zero is also an eigenvalue: the nonzero continuous function has both endpoint values zero, so .
For , the linear projection identity gives an explicit bounded inverse:
Multiplying on either side by yields . There are no other points in the spectrum, and thus the spectrum of a nontrivial bounded projection here is
Let , as calculated in part (ii). Its endpoint values ensure . Since for all ,
This verifies the spectral radius formula explicitly:

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