Prompt 3: The Cosine Rule 1

1. Which formula do you use for the cosine rule? A formula that isn’t listed above?

2. Why might you stress the importance of number 2?

3. Is there a context in which you would consider teaching number 3? Is it a problem that this doesn’t appear in textbooks or formula books?

2 thoughts on “Prompt 3: The Cosine Rule 1

  1. I think you’re missing a `^2` on the left-hand side of that third equation.

    In the first one, I would permute the variables so that `c` is on the LHS. This avoids the double `c` in `b c cos` (which when typing could also be avoided by using `\cos` instead of `cos` but I’d still avoid this because the distinction is harder to make in handwriting).


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