Difference between revisions of "1988 AJHSME Problems/Problem 9"
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Revision as of 08:09, 15 April 2009
Problem
An isosceles triangle is a triangle with two sides of equal length. How many of the five triangles on the square grid below are isosceles?
Solution
The first triangle has two legs of length , the second has two legs of length 2, the leg lengths of the third triangle are , , and , two legs of the fourth triangle have length , and two legs of the fifth triangle have length . Therefore all of the triangles in the diagram except the third are isosceles, and there are are isosceles.