Text-book of Euclid's elements for the use of schools : books I - VI and XI (1900)
Hall, H. S. (Henry Sinclair), 1848-1934, Stevens, F. H. (Frederick Haller), 1853-1933 · MacMillan : London · leaf 433
Note. It is proved in Proposition 3 that the common section oftwo planes is a straight line. Thus AB, the common section of the two planes PQ, XY is provedto be a straight line. 412 EUCLIDS ELEMENTS. 6. One plane is perpendicular to another plane whenany straight line drawn in one of the planes… … Thus in the above figure, the plane EB is perpendicular tothe plane CD, if any straight line PQ, drawn in the plane EB atright angles to the common section AB, is also at right angles to theplane CD. 7. The inclination of a plane to a plane is the acuteangle contained by two straight lines drawn…
Geometry · Mathematics
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