Started The Spy Who Came in from the Cold by John le Carré, which is fine so far, although I am getting tired of the 1950s/60s women character tropes.
I put Weak Heart on hold last week, but I might pick it back up again.
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Finished Foul Days by Genoveva Dimova. This was a fun, fast read about a witch who tries to regain her lost powers in a fantasy city, complete with creatures from Bulgarian folklore and a handsome detective. Somewhat similar in vibe and content rating as T. Kingfisher's fairy tale fantasies or early Robin McKinley, but with much thinner characterization. It did leave some loose ends for the sequel coming out in October, but not so many as to be obnoxious, imo. Oh, and sidenote: the informational pamphlet mentioned by the MC during the story was hidden at the end of my copy, so if you find the creature names confusing, hunt it up.
Bingo squares: New Release (HM); Eazy, Breazy, Read-zie; Debut Work; (alt) A Change in Perspective.
For a variation on this with fewer tangents (from A. S. Smogorzhevskii's The Ruler In Geometrical Constructions):
The issue, of course, is that any tangent you draw (without other circles, lines, or tools) is going to be approximate, and so the center will also be approximate. Every solution for this that I found just assumes accurate tangents, or parallel lines, or whatever, but I don't see a way to get those (I say, having only browsed through the topic briefly) when these two circles and a straightedge are all you have to work with. If that's not a big deal in your practical application, cool.
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** I'm shortcutting, here. The long version is to first draw two line segments, one that uses the smaller circle's tangent points (2) as endpoints, and one that uses the intersections on the larger circle (3) as endpoints. Because the two circles are concentric, these segments are parallel and centered on one another, so you end up with an isosceles trapezoid. You then draw its diagonals to get its midpoint.