Alsina, C.Monreal, A.2024-09-042024-09-042003-06-01Teaching Mathematics and Computer Science, Vol. 1 No. 1 (2003) , 153-1561589-7389https://hdl.handle.net/2437/379500We present a visual proof of the parallelogram law and using it we can describe a visual proof of a classical theorem on convex quadrilaterals relating sides and diagonals.application/pdfproof without wordsparallelogramquadrilateralsfolyóiratcikkOpen AccessC. Alsina and A. Monrealhttps://doi.org/10.5485/TMCS.2003.0003Teaching Mathematics and Computer Science11Teach. Math. Comp. Sci.2676-8364