Smith, David Eugene, 1860-1944 · Boston, New York [etc.] Ginn and Company · leaf 237
Gothic Designs employing Circles and Bisected Angles 225 226 THE TEACHING OF GEOMETRY The band maj~ either not be crossed (the case of the twoexterior tangents), or be crossed (the interior tangents),the latter allowing the wheels to turn in oppositedirections. In case the band is liable to change… … a third wheel, £>, is used. We then have the case of tangents to three pairs of circles. Illustrations of this nature make the exercise on the drawing of common tangents to two circles assume an appearance of genuine reality that is of advantage to the work.
Geometry
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