IB skill practice

Use sine rule and cosine rule

Choose and apply the sine rule, cosine rule, and triangle area formulae with clear formula reasoning.

Paper 1 6 marks Difficulty 2

Cosine rule practice

Two sides of a triangle are \(3\) and \(8\), with included angle \(60^\circ\). Use the cosine rule to find \(c^2\) and the missing side \(c\).

Worked practice: cosine rule

Substitute the included angle into the cosine rule, simplify c squared, then take the positive side length.