versine
/ˈvɜrsaɪn/
noun
- A trigonometric function equal to 1 minus the cosine of an angle, used historically in navigation and surveying.
- In the old textbook, the versine was listed alongside sine and cosine.
- The versine of a small angle is approximately half the square of the angle in radians.
- Navigators once used versine tables to calculate distances at sea.