This line is vertical and passes through the direct center. Imagine folding one side to have it land perfectly on the other side.
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Problem 3
The letter Z has rotational symmetry.
If we were to look at the letter, close our eyes, and then rotate it 180 degrees (or have a friend do so), we wouldn't see any difference if we opened our eyes again. The "before" and "after" images being identical is what gives it rotational symmetry. Put another way, rotating the letter 180 degrees has it line up with itself.
