Nine geometricall exercises, for young sea-men and others that are studious in mathematicall practices: containing IX particular treatises, whose contents follow in the next pages. All which exercises are geometrically performed, by a line of chords and equal parts, by waies not usually known or practised. Unto which the analogies or proportions are added, whereby they may be applied to the chiliads of logarithms, and canons of artificiall sines and tangents. By William Leybourn, philomath.

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Title

Author

Leybourn, William, 1626-1716.

Publication

London :: printed by James Flesher, for George Sawbridge, living upon Clerken-well-green,

anno Dom. 1669.

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http://name.umdl.umich.edu/A48344.0001.001

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"Nine geometricall exercises, for young sea-men and others that are studious in mathematicall practices: containing IX particular treatises, whose contents follow in the next pages. All which exercises are geometrically performed, by a line of chords and equal parts, by waies not usually known or practised. Unto which the analogies or proportions are added, whereby they may be applied to the chiliads of logarithms, and canons of artificiall sines and tangents. By William Leybourn, philomath." In the digital collection Early English Books Online 2. https://name.umdl.umich.edu/A48344.0001.001. University of Michigan Library Digital Collections. Accessed June 8, 2024.

Pages

I. How to protract (or lay down upon Paper) an Angle containing any number of Degrees and Minutes by the Line of Chords.

DRaw a right Line at pleasure, as A B, and from the Point A let it be required to protract or lay down an Angle containing 40 degrees.—First, open your Compasses alwaies to 60 degr. of your Line of Chords, (which is equal to the Line A C of the Quadrant,) and with this distance, set∣ting one foot of the Compasses upon the Point A, with the other foot de∣scribe the Arch B C.—Secondly, take in your Compasses 40 degr. (which is the quantity of the Angle to be laid down) out of the Line of Chords, from the beginning thereof, and setting one foot in B, the other will reach to C upon the Arch: where∣fore through the Point C draw the Line C A. So shall the Angle at A contain 40 degr. as was required.

[illustration] geometrical diagram