This exercise outlines a proof of the Pythagorean theorem

Chapter 1, Problem 100

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This exercise outlines a proof of the Pythagorean theorem that was discovered by James A. Garfield, the twentieth President of the United States. Garfield published the proof in 1876, when he was the Republican leader in the House of Representatives. We start with a right triangle with legs of length a and b and hypotenuse of length c. We want to prove that a2 b2 c2 . AT BU AT CS (a) Take two copies of the given triangle and arrange them as shown in Figure A. Explain why the angle marked u is a right angle. (u is the Greek letter theta.) (b) Draw the line segment indicated in Figure B. Notice that the outer quadrilateral in Figure B is a trapezoid. (Two sides are parallel.) The area of this trapezoid can be computed in two distinct ways: using the formula for the area of a trapezoid (given on the inside front cover of this book) or adding the areas of the three right triangles in Figure B. Compute the area of the trapezoid in each of these two ways. When you equate the two answers and simplify, you should obtain a2 b2 c2 .