Good morning Sonia! I hope you have made good progress in your revision! Here is my variant of the workings.
I used a basic angle’s triangle instead so that I do not have to worry about where to place the negative signs in the triangle. Instead, I place a negative sign afterwards in front of the sine, cosine or tangent based on my knowledge of A-S-T-C.
We use the double angle formula in both cases and we have to determine the direct quadrant in which the new angles lie in.
Let me know if you need more explanation and I will do my best to explain them again.
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