Cosine Rule trigonometry Question

Question

Do the following question twice, once using Pythagoras and the cosine rule and once using right triangle trigonometry.

Find, to the nearest degree, the size of the largest of the 3 angles of ΔABC where A, B and C have coordinates A (6,2), B (2,5), C (-6,-3)

Answer 1

1) Plot points

2) Determine length of AB, BC, and CA

3) Largest angle is opposite longest side

4) Use Law of Cosines to determine size of largest angle.

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