Manning, Henry Parker, 1859- · Boston, U.S.A., Ginn & Company · leaf 64
The angle A is the same in the plane triangle and in theboundary-surface triangle. The planes through A A are per-pendicular to ABC. Hence, the spherical triangle has a rightangle at the vertex which lies on c, and BC being perpendic-ular to CA is perpendicular to the plane of CC and AA.Therefore,…
Geometry, Non-Euclidean
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