You have hired a contractor to build a house. The rectangular foundation (the concrete slab that the house is built on) has just been finished. You want to make sure that the construction is done well and the foundation is square, so you decide to see if the corners are right angles. You measure the width of the foundation to be 30 feet, the length to be 72 feet and the diagonal to be 78 feet. Did the company build the foundation with right angles? Prove your answer (show your work)