Cosine Rule (cosine rule)
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cosine rule
What each symbol means
| Symbol | What it stands for |
|---|---|
| A,B,C | Opposite angles |
| a,b,c | Side lengths |
| R,r,s,Δ | Circumradius, inradius, semiperimeter, area |
When to use this
Valid for Euclidean triangle with positive sides satisfying triangle inequality.