Kenison, Ervin, Bradley, Harry Cyrus, 1871-1936 · New York : The Macmillan Company · leaf 179
n ofthis third plane with the given planes. Problem 27. To find the angle between two planes. First Analysis. From any point in space, drop a perpen-dicular to each of the given planes.The angle between* these lines isecpial to the angle between theplanes. Second Analysis. Let Q and R,Fig. 240, be… … Fig. 240. XVI, §145] PROBLEMS ON THE LINE AND PLAXE 159 between cs2 and cs3 is the required angle between Q and R.Let Ah be the projection of A on H. Since Z is perpen-dicular to A, Ah and .HZ are perpendicular (§ 111). Theprojection Ah and the trace HZ intersect in the point o ; con-nect c and o.…
Geometry, Descriptive
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