My older son is finishing up a chapter about right triangles in his Geometry book. The last section in the chapter discusses how to construct perpendicular lines. This topic has come up a few times previously, so I dedicated a bit more time to the previously section – Heron’s formula – before starting in with the new section this morning. I also left one of the examples in the book for him to work through as part of his homework.
One of the other homework questions was to construct a segment with length 
When I got home from work this afternoon I got a nice surprise:
Me: Were you able to construct the 30-60-90 triangle?
Him: That wasn’t one of the homework questions.
Me: Oh, I thought there was one about constructing a length equal to
Him: I made a 1 – 
Funny how focused your mind gets when you “know” how to do something. Wouldn’t have thought of this approach in a million years. Nice little construction!
Mike's Math Page 
I like that one ! In a few years he’ll be teaching you, and videoing it, and running a blog.