Past exam of the mathematics course of the University of Cambridge 2024 ib Paper 1 19H a Solution Created 2026-09-24 Updated 2026-09-25
Starting from , the probability of reaching before returning to is . Conditional on reaching , each visit to is followed by a hit on before the next return to with probability , by symmetry and the Strong Markov property. For , the number of visits after entry is therefore geometric on with mean . Hence the two-state excursion visit law givesIn the degenerate case , the chain never reaches before its return to , so almost surely and .