Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2005/iii/paper-5/3/ii/b/solution

The printed symbol is not defined. Take , or more generally an subspace with its induced norm; density must be in that norm. Given , choose a sequence with
By the assumed convergence on , each holds outside a null set . Their countable union is still null. Thus outside the convergence statements for every member of this single approximation sequence hold simultaneously. No assertion of simultaneous convergence for the entire uncountable dense class is needed.

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