Talk:Ptolemy's table of chords

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Untitled[edit]

I found a cite for "an earlier table of chords by Hipparchus gave chords only for arcs that were multiples of 7½°)" Paul August ☎ 02:15, 12 March 2011 (UTC)[reply]

Most, or maybe all, of the assertions are in the listed references, but I'd have to sort out which is which. I'll probably get to that in the coming weeks if no one beats me to it. Michael Hardy (talk) 02:36, 12 March 2011 (UTC)[reply]

Sixtieths[edit]

The details of the description of the meaning of the "sixtieths" column doesn't seem to make a lot of sense. How is it scaled? --Dfeuer (talk) 21:14, 7 July 2013 (UTC)[reply]

Arc vs. Chord[edit]

The article currently states "For tiny arcs, the chord is to the arc as π is to 3, or more precisely, the ratio can be made as close as desired to π/3 ≈ 1.04719755 by making θ small enough. Thus, for the arc of (1/2)°, the chord is slightly more than the arc."

This statement has the arc and chord reversed. The arc is always longer than chord since in Euclidean Geometry the shortest path between two points is a straight line. It should state: For tiny arcs, the arc is to the chord as π is to 3, or more precisely, the ratio can be made as close as desired to π/3 ≈ 1.04719755 by making θ small enough. Thus, for the arc of (1/2)°, the chord is slightly less than the arc. — Preceding unsigned comment added by 212.21.46.23 (talk) 11:00, 20 May 2014 (UTC)[reply]

The problem with the comments above is that the arc and the chord are measured in different units: the arc in degrees, i.e. 180ths of the semicircle, and the chord in 120ths of the diameter. If the arc length were 60 times the number of radians, then the comments above would be unproblematic. Michael Hardy (talk) 18:21, 4 June 2019 (UTC)[reply]