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 ...

The angles are labelled with capital letters. The opposite sides are labelled with lower case letters. Notice that an angle and its opposite side are the same letter. The sine rule is: \(\frac{a} ...

Now, a new article not only proves that theorem—which relies on the Law of Sines—but puts forth four more trigonometric proofs, as well as five additional proofs outside of trigonometry.