Today, my lecturer has come out with a question. He said creativity is required.
It took me a long time. However, I still unable to solve it. Perhaps, I have no creativity at all, haha. Well, after 30 minutes only one student solved it.
This question is quite interesting. It looks hard, but the solution is very simple.Now, I upload the question here and you can try to solve it.

Instruction:
1. Take out a piece of paper.
2. Draw nine dots as shown in the figure.
3. Connect all nine dots ONLY USING 4 LINES.
4. You are not allowed to lift up your hand.
5. Enjoy yourself.
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Maybe you need a hint. The hint is already stated at this post's title. So, can you solve it now?