Some days ago, our math teacher said that he would give a good grade to the first one that will manage to draw this:
To draw this without lifting the pen and without tracing the same line more than once. It's a bit like the "nine dots" puzzle but here I didn't find any working solution. So I have two questions:
- is it really impossible?
- how can it be proven that it is impossible (if it's impossible)
[EDIT]: After posting this question, and seeing how it was easy for people to solve it, I noticed that I posted the wrong drawing. The actual one is eaxctly like that but with triangles on all sides, not only top and bottom. As it would make the current answers invalid, I didn't replace the picture.