Versine
![A unit circle with trigonometric functions.](/Images/godic/202501/06/Unit-circle_sin_cos_tan_cot_exsec_excsc_versin_cvs.svg5439.png")
![Sine, cosine, and versine of angle θ in terms of a unit circle with radius 1, centered at O. This figure also illustrates the reason why the versine was sometimes called the sagitta, Latin for arrow.[32] If the arc ADB of the double-angle Δ = 2θ is viewed as a](/Images/godic/202501/06/Versine.svg5439.png")
![The trigonometric functions can be constructed geometrically in terms of a unit circle centered at O.](/Images/godic/202501/06/Circle-trig6.svg5439.png")
![Comparison of the versine function with three approximations to the versine functions, for angles ranging from 0 to 2π](/Images/godic/202501/06/Comparison_of_Versine_Approximations_for_Angles_of_0_to_2_Pi.svg5439.png")
The versine or versed sine is a trigonometric function already appearing in some of the earliest trigonometric tables. The versine of an angle equals 1 minus its cosine.
There are several related functions, most notably the coversine and haversine. The latter, half a versine, is of particular importance in the haversine formula of navigation.