Topic summary
Haversine
Extracted from the Wikipedia article Versine.
Haversine
The haversine, in particular, was important in navigation because it appears in the haversine formula, which is used to reasonably accurately compute distances on an astronomic spheroid (see issues with the Earth's radius vs. sphere) given angular positions (e.g., longitude and latitude). One could also use sin(θ/2) directly, but having a table of the haversine removed the need to compute squares and square roots.