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.

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} ...

But Jackson and Johnson managed to prove the theorem using a result of trigonometry called the Law of Sines, dodging circular ...