An elementary treatise on analytical geometry : embracing plane co-ordinate geometry, and an introduction to geometry of three dimensions (1869)
Johnson, William Woolsey, 1841-1927 · Philadelphia : J.B. Lippincott · leaf 268
ine.The sum of the projections ofthe co-ordinates upon the lineOP is therefore equal to OP or p. The projection of x upon OPis x cos a, because a is its inclination to OP. Hence, the value ofthis projection is p cos2 a. In like manner, the projection of y isp cos2 /?, and that of z is p cos2 y.… … * These direction angles may be represented by arcs of great circles uponthe surface of a sphere, in the following manner: The origin being thecentre of the sphere, let X, Y and Z be the points in which the positiveaxes pierce the surface; then XYZ is a tri-rectangnlar and tri-qundrantaltriangle;…
Geometry, Analytic
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