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The algebraic expression is certainly more compact. For example, suppose I have a regular pentagon and the side length is 15 cm. In the area expression A = 1.720 a^{2} the side length is represented by a. Thus in my pentagon a = 15 cm so the area is
I hope this helps,
A formula is simply a list of instructions. Your formula tells you to take the side of your pentagon, then square that number, then multiply the resulting square number by 1.720. This final number is the desired area. (Or, more correctly, it is the desired area accurate to about three decimal places.) Chris  


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