Find the point on y-axis which is at a distance of 
units from the point (1, 2, 3).
Given: point P(1, 2, 3)
To find: coordinates of the foot of the perpendicular from the point on the y-axis
Formula used:
The distance between any two points (a, b, c) and (m, n, o) is given by,
As x and z coordinate on the y-axis is zero
Let point D any point on y-axis be (0, y, 0)
⇒ PD2 = 10
Distance between P(1, 2, 3) and D(0, y, 0) is PD,
Now,
10 + (2 – y)2 = 10
⇒ (2 – y)2 = 10 – 10
⇒ (2 – y)2 = 0
⇒ 2 – y = 0
⇒ y = 2
Hence, coordinates of point D are (0, 2, 0)
10