2 = 23.59561414 \dotsc\). Do not round this answer yet. Use the form \(\cos{A} = \frac{b^2 + c^2 - a^2}{2bc}\) to calculate the angle. \(\cos{y} = \frac{4^2 + 6.9^2 - 4.2^2}{2 \times 4 \times 6.9}\) ...

The trigonometric ratios sine, cosine and tangent are used to calculate angles and sides in right angled triangles. We are now going to extend trigonometry beyond right angled triangles and use it ...