Proposition: https://mathcs.clarku.edu/~djoyce/java/elements/bookI/propI43.html[br][br]Try moving the point A around (top left corner)[br][br]This corresponds to an incorrect but interesting attempt to make a geogebra for this proposition[br][br]If the point A is to the right of point B, then you will see two parallelograms, one blue and one green. The theorem says that the two parallelograms are congruent