There are some further trigonometric functions that are found occasionally. Few people use them, but it avoids confusion if you know what they are.

The **chord** of an angle θ is the length of a line joining the ends of two radii of a circle of radius 1, and separated by θ. Equivalently, it is the base of an equilateral triangle where the equal sides are of length 1 and the angle between them is θ.

The **versed sine** of an angle, vers(θ) = 1-cos(θ).

The **haversine** or half versed sine of an angle,

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The **coversed sine** of an angle, covers(θ) = 1-sin(θ).