$1.$ The Cosine Rule can be used to find an unknown angle or length depending on the given conditi

Question

$1.$ The Cosine Rule can be used to find an unknown angle or length depending on the given conditions. $c^2 = a^2 + b^2 - 2ab \cos C$ $b^2 = a^2 + c^2 - 2ac \cos B$ $a^2 = b^2 + c^2 - 2bc \cos A$ $2.$ Conditions to use Cosine Rule: • Non right-angled triangle • When given 2 sides and 1 included angle • When given 3 sides

Accepted Answer

The Cosine Rule is $a^2=b^2+c^2-2bc\cos A$ (and its cyclic equivalents). Use it in a non-right-angled triangle when two sides and the included angle, or all three sides, are known.

Cosine Rule

Cosine Rule

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