Exercise 6.

How many triangles are there with vertices from the points shown below? Note, we are not allowing degenerate triangles - ones with all three vertices on the same line, but we do allow non-right triangles. Explain why your answer is correct.

Five equally spaced dots in a vertical line and six additional equally spaced dots extending to the right in a horizontal line from the lowest dot (forming a right angle).
Hint.Solution.
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