The versine or versed sine is a trigonometric function found in some of the earliest (Vedic Aryabhatia I) trigonometric tables.
The versine of an angle is 1 minus its cosine.
There are several related functions, most notably the coversine and haversine.
The latter, half a versine, is of particular importance in
the haversine formula of navigation
(source: Wikipedia)
```txt
d(vsin x) / dx = sin x d(cvsin x) / dx = -cos x
∫ vsin(x) dx = x - sin x + C ∫ cvsin(x) dx = x + cos x + C ```