This was another problem given to me by one of my math teachers that I don’t know how to solve.
Here it is:
We have a triangle $ABC$ and point $D$ is inside the triangle. Is it possible to assign integer lengths to $AB$, $BC$, $AC$, $AD$, $BD$, and $CD$, such that only one of these lengths has an even value? If it is possible what are the lengths and their configuration?
(I recently asked a separate question where $D$ is taken to be on side $BC$.)
I don’t have much work for this problem. I tried to isolate quadrilateral $ABCD$ from side $AC$ to try to use Euler’s quadrilateral theorem on $ABCD$, however I am unsure if this will work. This is because $ABCD$ is a concave quadrilateral and I don´t recall reading anywhere that Euler’s Quadrilateral Theorem works on concave quadrilaterals.
Other than this, I don’t have any ideas to solve this problem, so please help.