Aldis, W. Steadman (William Steadman), 1839-1928 · Cambridge [Eng.] Deighton, Bell, and co.; London, G. Bell and sons · leaf 15
I, in, n are frequently used to denote cos a, jcos)3, cos 7, which are called the direction-cosines of the lineOP. It is usual to denote by a, [3, 7 the angles which OP jmakes with the positive directions of the axes, in which casethe formula) (2) hold for all positions of the point P. INTRODUCTORY… … parallel to each of the co-ordinate planes, thus forming aparallelepiped whose edges are parallel to the co-ordinate axes,and are equal in length to x^ — x^, y^ — y^, z^ — z^, respectively. As in Art. 4, we obtain PQ^ = PH + HN^ + NQ^ = (^,-^,y4-(y,-y,y + (^,-^,)^ (4). We have also formulse similar…
