The Sine and Cosine Rules (Edexcel GCSE Maths): Flashcards

Non-right-angled triangles

Lowercase

Uppercase

Each side has same letter as opposite angle

$\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}$

$a^2 = b^2 + c^2 - 2bc \cos A$

$\cos A = \frac{b^2 + c^2 - a^2}{2bc}$

$\frac{1}{2}ab \sin C$

Sine rule

Sine rule

Cosine rule

Cosine rule

Ambiguous case - may have 2 solutions

180°