Suppose I say, "I walked from A to B along the arc of the circle with center O."
Let us agree the arc was traversed from start to finish in a single direction.
Given A, B, and O,
[i]Draw it.[/i]
Go on.
....
{It cannot be done. There are two choices.}
...
We can tell a little story in our heads where I can only walk in one direction, but that's pretend.
Here is a better way: disambiguate. There are at least two ways:
1. Sign: "In what direction?"
2. Name a waypoint on the arc.
I say, [i]the arc is now uniquely determined[/i].
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Measuring angles and arcs
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