Hour of Math · SS2 · Unit SSGM9

The Cosine Rule — Finding a Missing Side

Explain why the sine rule fails for SAS, follow the derivation of the cosine rule for acute and obtuse triangles, state all three forms, and apply $a^2 = b^2 + c^2 - 2bc\cos A$ to find the third side when two sides and the included angle are known.

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