Lesson 4 of 4 · Form 3 Mathematics
The sine and cosine rules
18 min
For any triangle ABC, side a is opposite angle A, and so on.
Sine rule
a/sin A = b/sin B = c/sin C
Use when you know: two angles and a side, or two sides and a non-included angle.
Cosine rule
a² = b² + c² - 2bc cos A
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