question_answer 1)

If a line makes angle 90°, 135°, 45° with the positive x, y and z-axis respectively, find its direction cosines. 

Answer:

Let l, m and n are the direction cosines of given lines          l = cos 90° = 0             m = cos 135° = cos (180 ? 45°)             = ? cos 45° =             and n = cos 45° =              direction cosines are 0,