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A carpenter is building a bookcase. How can she use a tape measure to check that the bookshelf is rectangular? Justify your answer and name any theorems used.

2007-04-05 16:19:49 · 2 answers · asked by Anonymous in Science & Mathematics Mathematics

2 answers

Using a tape measure, the carpentar can measure the diagonals of the book shelf to see if they are the same. Only rectangles and squares (also a rectangle) have congruent diagonals.
Look in your book at whatever theorem says

"If the diagonals of a quadrilateral are congruent, then the figure is a rectangle."

2007-04-05 16:25:37 · answer #1 · answered by Big D's Tuna 2 · 1 0

A standard method is to use the "3-4-5" triangle. A right triangle with legs of 3" and 4" will have a hypotenuse of √3^+4^2 = √9+16 = √25 = 5". (or cm, or feet, or any consistent measurement unit). So mark off 3" from a corner on (e.g) he side, 4" from the same corner on (e.g) the top, and measure the distance between the marked points. When it is 5", the corner is 90º. Do this for each corner, readjusting until all corners meet the "3-4-5" rule.

2007-04-05 16:28:01 · answer #2 · answered by gp4rts 7 · 0 0

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