Hi Mike. I had a question about problem 3 on page 284 of your PWN 4th edition book. I don’t understand how you can put values of a, b, c, or d on to the sides. How do you determine which side is which letter?

The trick here is recognizing that d appears three times in the expression ab+ad+bd+cd. That tells you that d must be the height, which is part of the area of each of the three vertical sides.

Once you know that, you can determine that the area for ab, the only term without a d must be the top and the bottom areas. This means that the top and bottom triangles must each be \dfrac{1}{2}ab. And that means that these must be right triangles, with legs a and b. And if a and b are legs, then c must be the hypotenuse—AKA the longest edge of the base.

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