Coversine

$$\mathop{\rm covers}A\equiv 1-\sin A,$$

where $\sin A$ is the Sine.

See also Exsecant, Haversine, Sine, Versine

References

Abramowitz, M. and Stegun, C. A. (Eds.). Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, p. 78, 1972.