Tag Archives: Law of Cosines

On 2012 Putnam problem A1

The Putnam competition was last weekend, on December 1. I was coaching Smith’s team this year, so I’d like to go through solutions to each of the problems (or as many as I can solve), with my students being the intended audience. But I’ll post the solutions on this blog, since I’m sure they’ll be of interest to a wider audience.

I’ll start with the first one, Problem A1. It’s often the case that Putnam problems can be solved in several different ways, but sometimes you discover a solution that is clearly the most elegant of all possible approaches. That’s the case with this one, although I will include greater-than-necessary detail for pedagogical purposes.

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