Use the Pythagorean Theorem: [tex]a^2 + b^2 = c^2[/tex]
You can do this because when you cut the rectangle in half with the diagonal, it forms a right triangle, making the diagonal the hypotenuse (c).
[tex]40^2 + 48^2 = c^2[/tex]
[tex]1600 + 2304 = c^2[/tex]
[tex]3904 = c^2[/tex]
[tex] \sqrt{3904} = \sqrt{c^2} [/tex]
[tex]62.48 = c[/tex]
Diagonal: 62.48 inches
