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A pattern continues forever in both directions.
Imagine it's on a roll of paper and two strips are torn off, one of which is turned upside-down and placed underneath the other.
It is not possible to shift the lower strip horizontally so that it lines up and matches the upper strip.
This problem is about that kind of symmetry.
The pattern is a trace from a point on a rolling wheel.
Before starting, you may find it useful to explore How far does it move? .
Point 1 is on the circumference of the wheel and its trace looks like this:
Forget the wheel for a moment and just concentrate on the trace pattern.
If this trace was turned upside-down you would certainly not be able to line it up with itself.Point 2 is somewhere inside the wheel and its trace looks like this :
Would "Trace Two" line up with itself upside-down?
Justify your answer, if you can.
The third trace is made where a horizontal line from Point 1 intersects with a vertical line through the centre of the wheel. It looks like this :
Can "Trace Three" line up with itself upside-down?Justify your answer this time.