coversine
/ˈkoʊvərˌsaɪn/
noun
- A trigonometric function equal to 1 minus the sine of an angle; used mainly in historical mathematics and navigation.
- The coversine of 30 degrees is 0.5.
- In old navigation tables, the coversine helped sailors calculate distances.
- The student learned about the coversine while studying the history of trigonometry.