2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/95648Let $A$ be an arc on the boundary of the unit disk $U$. We prove an asymptotic formula for the probability that there is a percolation cluster $K$ for critical site percolation on the triangular grid in $U$ which intersects $A$ and such that 0 is surrounded by $K\cup A$.7 pages; minor changes from previous versionProbabilityMathematical Physics60K35; 82B43text