Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 122
iv). THEOREM VII. If one panc intersect another plane, the sum of the angles onhe same side will be equal to two right angles. Let the plane GEF intersectthe plane AB in the line FE :then will the sum of the twoangles on the SMne side be equalto two right angles. ! or, from any point, as E, inllio… … 12J GEOMETRY. Of Planca equal to two right angles (Bk I.Th. ii): but these angles measurethe inclination of the planes ; there-fure, the sum of the angles on thesame side, which two planes makewith each other, is equal to tworight angles. Cor. In like manner it may be demonstrated, that planeswhich…
Geometry · Plane trigonometry
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