Find the Diagonal of a Rectangle
Date: 07/26/97 at 05:16:59 From: Boyd Henderson Subject: One very confused crew Dr Math I am a building contractor and one day during lunch someone asked how to find the diagonal of a rectangle. We use a tape measure to square different things on the job site by measuring corner to corner and then again on the opposite corners. I have tried to think it through and recall some of that high school geometry but it was just too long ago. Could you please help? I know that it is not as tough as I am making it. Thanks. Boyd Henderson
Date: 07/26/97 at 09:17:15 From: Doctor Jerry Subject: Re: One very confused crew Hi Boyd, Carpenters, whether they remember the Pythagorean Theorem or not, use this classical theorem when they use a tape measure to square various corners on the job. Think of the rectangle as a piece of paper. Suppose the lengths of the sides are a = 8.5 by b = 11. Draw the diagonal on the paper. Let its length be c. The Pythagorean Theorem (for either of the triangles on opposite sides of the diagonal) says that a^2+b^2=c^2 (a^2 means a*a or a squared). So, c^2 = 8.5^2+11^2 = 72.25+121 = 193.25. This is c^2. To calculate c, take the square root of 193.25, which is 13.90, approximately. -Doctor Jerry, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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