A line makes angles of 45° and 60° with the positive axes of x and y respectively. What angle does it make with the positive axis of z?
Let P(– 1, 2, – 3), Q(4, 5, 1) , R(9, 8, 5) be given points.
The direction ratios of PQ are 4 + 1, 5 – 2, 1 + 3 i.e. 5, 3, 4,
The direction ratios of PR are 9 + 1, 8 – 2, 5 + 3, i.e. 10, 6, 8.
Since
∴ lines PQ and PR are parallel.
But P is a common point on both lines.
∴ points P, Q, R are collinear.
Find the length of the projection of the line segment joining the points P (3, -1, 2) and Q(2, 4, -1) on the line with direction ratios -1, 2, -2.