Coordinates are not show however Larissa would need to prove that the slope of the diagonals are negative reciprocals of each other. For example if the slope of one diagonal is 1/2, the other diagonal should be -2/1. To find slope for each diagonal assign coordinates values of (x1,y1) and (x2,y2) then subtract y2-y1 and x2-x1. Then divide the change in y by the change in x for each line. The coordinates are the endpoints of each diagonal, the vertices of the square.