## Elementary Geometry for College Students (6th Edition)

We place the rectangle at the origin, giving it length a for its short sides and length b for its long sides. Using the Pythagorean theorem, we obtain: $(d_1)^2 = a^2 + b^2 \\ (d_2) ^2 = a^2 +b^2$ Combining these gives: $(d_1)^2 = (d_2)^2 \\ d_1 = d_2$ Hence, the diagonals are equal in length.