+283 How many different non-congruent isosceles triangles can be formed by connecting three of the dots in a 4x4 square array of dots like the one shown below?
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Two triangles are congruent if they have the same traced outline, possibly up to rotating and flipping. This is equivalent to having the same set of 3 side lengths.
The answer is not 9 or 3.
+998 I'm not sure. I've done the same exact problem somewhere else before, but I do not recall the answer.
Here is a similar question: https://artofproblemsolving.com/wiki/index.php?title=2009_AMC_8_Problems/Problem_20
Maybe like the question above, sort them by base lengths, and see how many triangles can be formed by connecting points from each distinct base length.
