versed sine

versini puhekieltä The trigonometric function 1 − cos(x).
1753, John Robertson, The Construction of the Logarithmic Lines on the Gunter′s Scale, Royal Society (Great Britain), Philosophical Transactions: 1750-1755, http://books.google.com.au/books?id=RUVJAAAAYAAJ&pg=PA340&dq=%22versed+sine%22%7C%22versed+sines%22&hl=en&sa=X&ei=phSRUMr3DLGdiAfI4YGAAQ&ved=0CFQQ6AEwCwv=onepage&q=%22versed%20sine%22%7C%22versed%20sines%22&f=false page 340,

For the divisions, to be laid on this line, are the differences between the logarithm versed sine of 180°, and the logarithm versed sines of the successive arcs.

But if the given arch exceed 90°, find the natural co-sine of its supplement, which add to 1000000, and the sum will be the natural versed sine required.

The Natural Sines in this table are fractions (radius being unit); and are particularly adapted to Dunthorne′s and other methods of clearing the moon′s distance from the effects of parallax and refraction, where natural sines or versed sines are used ;(..).