Correct Answer - Option 3 : 3
Concept:
The projection of any point on (a, b, c) on x -axis is (a, 0, 0), y-axis is (0, b, 0) and z-axis is (0, 0, c).
Calculation:
The projection of A(1, 7, -5) on y-axis is (0, 7, 0) and projection of B(-3, 4, -2) on y-axis is (0, 4, 0).
Let C = (0 ,7, 0), D = (0, 4, 0) and O = (0, 0, 0) is the origin
⇒ OC = 7 and OD = 4
Let the projection of line segment AB is m = OD - OC.
⇒ m = OD - OC = 7 - 4 = 3
Hence, correct option is 3.