# RectangleFind the diagonal of a rectangle whose length is 8 inches and whose width is 5inches.

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Let d = diagonal, l = length, w = width

Since we know that the diagonal of the rectangle splits the rectangle into two right angle triangles, being the hypotenuse of both right angle triangles.

To compute it's length, we'll apply the Pythagorean identity:

d^2 = l^2 + w^2

d^2 = 64 + 25

d^2 = 89

d = sqrt 89 units

We'll reject the negative value, since a dimension cannot be negative.