Geometry

What is DE ?

$\overline{BC}^2=\overline{AB}^2+\overline{AC}^2-2\cdot \overline{AB}\cdot \overline{AC}\cdot cos\ \alpha\\ \alpha =acos\ ( \dfrac{\overline{AB}^2+\overline{AC}^2-\overline{BC}^2}{2\cdot \overline{AB}\cdot \overline{AC}})\\ \alpha =acos\ (\dfrac{13^2+19^2-3^2}{2\cdot 13\cdot 19})=acos\ (1.0546\ ...)\\ \alpha =\ unreal$

The segments 3, 13 and 19 do not form a closed triangle.

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