Just make sure to draw them from the midpoints of the two edges!
It surprises me how many people don’t use or don’t even know about Explode Arc Lines To Arc.
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So what are the less obvious benefits of converting lines to an arc rather than welding?
Good point, Steve - I should have mentioned that!
@Box Thank you for the nice demo. I am aware of such plugins. In some ways I am a non-rational curmudgeon who avoids using plugins unless they provide more than some threshold of value to me. 
I confess to having spent a modest amount of time trying to convince SketchUp to re-classify a set of edges back into a circle.
My usual method, when dealing with Follow Me constructions on circular paths, is to create the follow-me entities in separate space, unconnected to the main model geometry. Put a circle on the main geometry where I want an edge of the final follow-me geometry to lie. Then move the constructed geometry on top of the main geometry and its circle. Often/usually SketchUp will preserve the pre-existing circle entity, when dealing with the now-overlapping follow-me edges.
The next time I’m facing that situation, I shall re-evaluate my approach to a solution.
Do you mean that SketchUp recognizes the arc as an arc and a circle as a circle instead of a curve?
Depends on what you consider “obvious”. 
Besides the fact that SketchUp can find the center of arcs and circles (but not generic curves, despite being arranged into circular paths), I just enjoy being able to select the compound set of edges and see that SketchUp shows a circle or arc entity! It reflects the modeled intent.
me too.
By obvious I meant they can be selected in situ easily as one entity.
I won’t repeat the others, but Cardinal points work again.
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When extruded they don’t leave a bunch of hard edges.
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I was testing the cardinal point function on a circle and learned that they (cardinal points) can’t be used on circles that are selected. That had me stumped for a bit.
That would be kinda the point of cardinal points.
As have many of us!
There is an interesting asymmetry in SketchUp’s handling of arcs: it will tolerate an arc that has come to have unequal length end segment(s) due to editing, but it can only create an arc with equal length segments! That means that if you naively regenerate the arc based on the center, radius, start and end points, etc., the segments and vertices will be replaced with a new set that don’t match the originals! As a result, other edges that originally intersected the arc will probably not intersect the replacement!
I haven’t tested whether the various extensions overcome this fact, e.g. by extending the end segments back to length to find the end vertices, generating the arc, and then trimming them back down.
Edit: the one @Box referenced does not. It requires equal length edges.
Partly to deal with irregularities such as what you mentioned, lately I am more and more using your Circle Intersect extension to determine the precise span of a nice uniform arc, rather than start with a circle or approximated arc and cut it up (deleting the unwanted ends).
Sometimes I catch myself thinking, wouldn’t it be great if we had these conversation on a forum that the developers of the software had access to!
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Yes actually. What are the differences between an arc and a curve if they are the same shape? Maybe this isn’t the place to learn that.
An arc has associated metadata containing the defining math parameters of the circle it belongs to: center, radius, normal vector of plane, number of segments, start and end angles. A curve is just a welded-together sequence of edges.
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Yep, it really only works with exploded curves that haven’t been modified, ie; the segments are still the same size. having said that you can re-arc a section of a curve if need be.
Tdahl - Thank you for suggesting the context menu! All these years I have been using Sketchup and I didn’t even know that feature was there!
Ian McIlvaine
Tierra Sol y Mar, Inc.
601 Rose Ave.
Venice, CA 90291
cell: 310-497-7022
Wow!