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 460
is par1 to AC, a side of the A DAC, .. AX : XD :: CF : FD. VI. 2. Hence AE : EB :: CF : FD. v. 1. Q.E.D. Definition. One plane is perpendicular to anotherplane, when any straight line drawn in one of the planesperpendicular to their common section is also perpendicularto the other plane. [Book xi.… … Let the st. line AB be perp. to the plane XY;and let DE be any plane passing through AB. Then shall the plane DE be perp. to the plane XY. Let the st. line CE be the common section of the planesXY, DE. XI. 3. From F, any point in CE, draw FG in the plane DEperp. to CE. I. 11. Then because AB is…
Geometry · Mathematics
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