Question 668437
Find the interior angles of the triangle with vertices A=(3,2), B=(4,5), C=(-1,-1)
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One way is to find the lengths of the 3 sides, then use the Cosine Law.
Can you do that?
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Another is to find the slope of each side and then find the angles.  Less work than the 1st method.
Do you know how to do that?