Question
Find the angle between each of the following pairs of lines:
A line with direction ratios 2 : 2 : 1.
A line joining (3, 1, 4) to (7, 2, 12)
Solution
Direction-ratios of first line are 2, 2, 1.
Direction-ratios of second line joining the points (3, 1, 4), (7, 2, 12) are 7 – 3, 2 – 1 12 – 4 i.e., 4, 1, 8
Let θ be the angle between the two lines
