Angle bisector theorem

[tomergal]

I’m wondering what’s the CCSS stance about the angle bisector theorem. I guess that proving this kind of falls under G-SRT.4 But what about using the theorem when solving geometrical problems?

[johnrmead]

The Angle Bisector Theorem always stood out to me as one of those tricks that can be useful in solving specific problems, but which had relatively few useful applications in authentic problems. I think of it as a good candidate for analysis under G-SRT.4 but it is more like a trick than a useful general tool. It’s another vestigial relic in our curriculum from Elements that, even in the original, served as a dead end rather than as a foundation to other work.

[Author]

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