You can put this solution on YOUR website! It isn't entirely clear what you mean by the length of a "short cut" across the rectangle.
Do you mean the length of the diagonal (a line that connects opposite corners)?
Let's assume that this is really what you are looking for.
The length of the diagonal of a rectangle can be found using the Pythagorean theorem when you are given the length (L = 171 ft.) and the width (W = 52 ft.)
Let's call the diagonal, d, then... Substituting L = 171 and W = 52,... ft.
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