Circle/polygon tool with ALTERNATIVE radius

[GuruMonkey]

Is there an existing plug-in to change the radius of polygons
FROM the apex points of the outer sides
TO being perpendicular to the line segments

This would be useful when attempting to draw the octagon in the 1st attached picture.

I am currently achieving the desired result by drawing an over sized octagon, rotating it 22.5°, then re-scaling it about the centre-point until it fits at a very zoomed in view.
or just reverting to maths on paper...

This would be very useful for the above use case (see attached pic)
but also, as circles are approximated by polygons, the current setting is stuck on showing the maximum radius of the approximated circle, though sometimes the minimum would be more useful. (again, better explained by the picture attached)

Thanks!
Mike

[Box]

Can't see your images just now, but have you tried hitting ctrl with the polygon tool.

[Box]

Is this the sort of thing you want, where the flat rather than the vertex is set as the radius.

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[Dave R]

Box is on it but... What version of SketchUp are you using? Your profile indicates 2014. Is that correct? I don't believe the inscribed/circumscribed option had been introduced yet.