Friday, June 19, 2015

Geometric Translations

Recently inspired by some posts on problem solving over at I've been combing through the geometry problems at  So far the first 7 or so have been really interesting. I spent several days on the first one or two and went down several blind alleys. I've become used to relying on similar triangles and basic angle chasing for most geometry problems.  Most of these problems require triangle rotation/translation instead to make headway.


My final solution required three such rotation/translations. First ABD is translated inside BDC. Then the smaller new triangle is translated twice more and you find an unexpected equilateral triangle.

The complexity here also puts this beyond the kids in math club's skill set. However, I think there's the start of an interesting exercise for the day present in these type of problems.  Translation is not done much in school but is very simple to describe and then opens up lots of interesting areas. One of my favorite transforms is to take the two triangles created by the median of a triangle and then recombine them by sticking the divided edge together into a new but related triangle. These also can be thought of as tiling exercises. So I'm off to see if I can find a range of problems or activities that would be approachable.

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