Haversine

$$\mathop{\rm hav}(z)\equiv {\textstyle{1\over 2}}\mathop{\rm vers}(z)={\textstyle{1\over 2}}(1-\cos z),$$

where $\mathop{\rm vers}(z)$ is the Versine and cos is the Cosine. Using a trigonometric identity, the haversine is equal to

$$\mathop{\rm hav}(z)=\sin^2({\textstyle{1\over 2}}z).$$

See also Cosine, Coversine, Exsecant, 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.