File:Compas de proportion 1.jpg

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Description
English: Typical English sector made by the Dollond family firm of London, probably circa early 19th century, constructed of ivory with a brass hinge. This side shows four double scales, repeated on each of the sector's two legs. These scales are the line of lines (labeled L, marked from 1 to 10), a linear scale used for general proportion problems; the line of secants (labeled S, marked in degrees from 20 to 75), for finding the secant of a given angle; the line of chords (labeled C, marked in degrees from 10 to 60), for finding a given angle from a circle of known radius; and the line of polygons (labeled POL, marked from 12 out to 4), for inscribing within a circle a regular-sided polygon of the given number of sides. The L and C scales have their zero point at the sector's hinge; the S scales' zero point is at the 2.5 point on the L scales. Except for the POL scale, all the double scales are arranged so that they form the same-sized angle when the sector is opened a given amount, to make it easier to perform calculations that need more than one scale. A split scale of 12 inches is also present along the outer edges.
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Author Fgrosshans
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  • Other side of this instrument
    Other side of this instrument

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I, the copyright holder of this work, hereby publish it under the following licenses:
GNU head Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.
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current22:33, 30 October 2007Thumbnail for version as of 22:33, 30 October 20073,868 × 1,072 (823 KB)Fgrosshans (talk | contribs){{Information |Description= sector (instrument) |Source=travail personnel |Date=30 o |Author= Fgrosshans }}

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