Aldis, W. Steadman (William Steadman), 1839-1928 · Cambridge [Eng.] Deighton, Bell, and co.; London, G. Bell and sons · leaf 17
iihirly it may be shewn that i\ + n^ y n, + n^ INTRODUCTORY THEOREMS. If R be the middle point of PQ, n^ — n^, and we have 5j^ ._ 2/1 + 3/2 ^ ~ 2 ^ ~ 2 /_^i+^2 8. To ^?icZ ^/le angle between Uuo straight lines whosedirection-cosines are given. Since by Euclid, xi. 10, the angle between any two… … of OP; V, m, n those of OQ. Let x^, y^, z^, be the co-ordi-nates of P any point in OP; x^, y^, z^ those of Q any pointin OQ. Then by Art. (6) -p«^=K-^ir+(2/2-2/j+(^2-^j =<+y+< + < + y + ^1 - 2 {x,x^+y,y, + ^x^J- But by Art. (4) x: + y: + z,=OP\ x:+y:^z:=oQ\ 8 INTRODUCTORY THEOREMS. And by…
