Trigonometry teachers HATE HIM

One weird trick! Click here!

Somewhere in my years of “tutoring calculus,” also sometimes referred to as “tutoring trigonometry,” I discovered a trick (here meaning a tool devoid of any conceptual knowledge of the topic at all) for evaluating the cosine (and therefore also sine) of the upper-right quadrant special angles 0, \pi/6, \pi/4, \pi/3, \pi/2. This can be extended to the rest of the unit circle in the usual way.

I rarely see this move discussed, and it is such an easy way to “memorize the unit circle” that I find this surprising. As with all academics, I should be writing, so here you go.

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