Larissa is writing a coordinate proof to show that the diagonals of a square are perpendicular to each other. She starts by assigning coordinates as given. A square is graphed on a coordinate plane. The horizontal x-axis and y-axis are solid, and the grid is hidden. The vertices are labeled as K, G, H, and J. The vertex labeled as K lies on begin ordered pair 0 comma 0 end ordered pair. The vertex labeled as G lies on begin ordered pair 0 comma a end ordered pair. The vertex labeled as J lies on begin ordered pair a comma 0 end ordered pair. One vertex is unlabeled. Diagonals KH and GJ are drawn.

Enter the answers in the boxes to complete the coordinate proof.