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Lesson on cosine rule

Answer Text:
According to this rule; For the given triangle below.

`a^2 = b^2 + c^2 – 2bc Cos A.`
`b^2 = a^2 + c^2 – 2ac Cos B.`
`c^2 = a^2 + b^2 – 2abCos C`
Note; The cosine rule is used when we know
- Two sides and an included angle
- All three sides of a triangle