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