I find some students like to memorise this, or at least the first two or three rows and then remember that we keep adding 180 for extra size.
Reason being – an extra triangle.
I feel that using exterior angles is more satisfying. I find myself walking around an imaginary hexagon in my classroom with arm out stretched.
Here’s an activity which reinforces this idea. Use a pencil as an arrow. Does it always rotate through 360? Does it always turn the same direction? Use algebra, maybe?
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