Abstract: Research on teaching and learning proofs in linear algebra is scarce. This paper used the instrumentation genesis approach to examine students’ proofs and MATLAB codes. The students were studying a proof-based second course in linear algebra. The instructor included application-focused labs and a final project as part of this study. One of the labs required a proof validation using MATLAB. This lab, a proof question from the midterm exam, and an exit survey were analyzed in this paper.