[Strilanc]

The really interesting thing about this video, to me, is the explanation of how tangents were calculated before calculus. You can see how awkward it would have been to do things that way, and how it would have been difficult to realize they was something far far easier.

[29athrowaway]

Trigonometric functions have existed for a long time. And in the past, more trigonometric functions were used:

- versed sine (versin) and versed cosine (vercos)

- coversed sine (coversin) and coversed cosine (covercos)

- haversed sine (haversin) and haversed cosine (havercos)

- hacoversed sine (hacoversin) and hacoversed cosine (hacovercos)

- exsecant and excosecant

Perhaps I am forgetting some. Many alternative mnemonics exist for these too.

This formula was very important: https://en.wikipedia.org/wiki/Haversine_formula