Arrow-chasing in Pascal's triangle -- Visual proofs for summation formulas involving binomial coefficients

Abstract: This article demonstrates, using numerous examples of varying complexity, how one can visually prove summation formulas involving binomial coefficients by exclusively using the recurrence relation for binomial coefficients and its illustration through arrows in Pascal's triangle. The method developed for this purpose, which we call "arrow-chasing", is elementary and it is accessible to a very broad audience.