Smith, David Eugene, 1860-1944 · Boston, New York [etc.] Ginn and Company · leaf 253
i:;« The Quadrant used for DistancesBettinuss Apiaria universae philosophiae mathematicae, Bologna, 1645 242 THE TEACHING OF GEOMETRY The quadrant finally developed into the octant, asshown in the following illustration from Hoffmann, andthis in turn developed into the sextant, which is now usedby… … The OctantHoffmanns De Octantis, Jena, 1612 In connection with this general subject the use ofthe speculum (mirror) in measuring heights should bementioned. The illustration given on page 243 showshow in early days a simple device was used for this pur-pose. Two similar triangles are formed in this…
Geometry
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