Aldis, W. Steadman (William Steadman), 1839-1928 · Cambridge [Eng.] Deighton, Bell, and co.; London, G. Bell and sons · leaf 40
find the shortest distarice between tiuo straightlines whose equations are given. We must first prove that the shortest line between two11 given straight lines is perpendicular to each of them. 30 THE STRAIGHT LINE AND PLANE. Let BC, ^D be the two straight lines, and AB a lineperpendicular to each… … P D PA and QB are both perpendicular to AB, and therefore ABis the projection of PQ on AB, and is equal to the lengthof PQ multiplied by the cosine of the angle between them,and is therefore less than PQ, since the cosine of any angleis less than unity. —=^_^.i- a). x-a _y-^ _z-r^ A B a ^ ^ be the…
