Godfrey, C. (Charles), 1873-1924, Siddons, A. W. (Arthur Warry) joint author · Cambridge, University Press · leaf 134
ake the case of projection on to a horizontal plane from aplane inclined to it at 60°. Prove that all the lines of steepest slope are halved by projection. Are any lines unaltered by projection ? What is the condition that two lines that are equal before projection shallremain equal after… … fig. 66. AB is the segment a, CD is its projection.In the plane AEC draw BF || to DC, meeting AC in F.Then LABf = LAEC = 0,.. DC = BF = aco8^, 8—2 116 ORTHOGONAL PROJECTION 5. Lines parallel to the plane of projection are un-altered in length by projection. 6. If A be an area in a plane, its…
Geometry, Modern
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