In the triangle ABC, AB equals 20, AC equals 12, D is the middle line, and ad equals 8, find the length of BC

Let the midpoint of AB be e, and connect De to get: de = 1 / 2Ac = 6, AE = 1 / 2Ab = 10, ad = 8
So △ ade is a right triangle, ∠ ade = 90
So, DAC = 90
So there is Pythagorean theorem, we can get CD = 4 radical 13, that is BC = 8 radical 13

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