If the co-ordinates of the points A, B, C, D be (1,2,3),(4,5,7) (-4,3,-6) and (2,9,2) respectively, then find the angle between the lines AB and CD

Answer

Direction ratios of AB are 4-1, 5-2, 7-3 i.e., 3, 3, 4 and the direction ratios of CD and 2+4, 9-3, 2+6 i.e., 6, 6, 8
Since 3/6 = 3/6 = 4/8, AB and CD are parallel `rArr` Angle between AB and CD = `0^@`