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T. Sundara Row's geometric exercises in paper folding. Edited and rev. by Wooster Woodruff Beman and David Eugene Smith (1901)

Sundara Rao, Tandalam, 1853-, Beman, Wooster Woodruff, 1850-1922, Smith, David Eugene, 1860-1944 · Chicago Open Court Pub. Co · leaf 66

An illustration from T. Sundara Row's geometric exercises in paper folding. Edited and rev. by Wooster Woodruff Beman and David Eugene Smith, 1901, leaf 66
f the nonagon. 98. OA = \a, where a is the side of the square; itis also the radius of the circumscribed circle, R. The radius of the inscribed circle = R . cos 20°= \a cos 20° = ~ X0.9396926 = tfX0-4698463.The area of the nonagon is 9 times the area ofthe triangle AOL = 9-^-£i?sin40o= § R2- sin… … Fig. 36. The main part of the process is to obtain theangles at the center. In Fig. 36, the radius of the inscribed circle ofthe pentagon is taken for the radius of the circum-scribed circle of the decagon, in order to keep itwithin the square. 48 GEOMETRIC EXERCISES ioo. A regular decagon may also…

Geometry -- Study and teaching · Paper work

Internet Archive · University of Toronto, Robarts Library · Public Domain Mark 1.0. Free to use for anything.

More pictures from T. Sundara Row's geometric exercises in paper folding. Edited and rev. by Wooster Woodruff Beman and David Eugene Smith

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