SOLUTION: D(5, 7), E(4, 3), and F(8, 2) form the vertices of a triangle. What is m DEF?

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Question 891900: D(5, 7), E(4, 3), and F(8, 2) form the vertices of a triangle. What is
m DEF?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Assuming the triangle might not be a Right Triangle, find the distances or lengths for DE, EF, and FD, and use Law Of Cosines.

If you just use some variable, m for the angle DEF, then form:
highlight_green%28%28EF%29%5E2%2B%28ED%29%5E2-2%28EF%29%28ED%29%2Acos%28m%29=%28DF%29%5E2%29;
solve for m.