The Cosine Rule (HSC SSCE Mathematics Standard): Flashcards

Any triangle, not just right-angled triangles

Two sides and the included angle

All three sides

The angle between two sides

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

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

Degree mode

Inverse cosine ($\cos^{-1}$ or arccos)

SAS (Side-Angle-Side)

SSS (Side-Side-Side)