Find the co-ordinates of the foot of the perpendicular
drawn from the origin. x + y + z = 1

Answer

The direction cosines of the normal to the plane are `(1)/sqrt3, (1)/sqrt3, (1)/sqrt3,` and the distance of the plane from the origin `= (1)/sqrt3` (see example 1(b) above)
`therefore` The foot of the perpendicular drawn from the origin `= (1/3, 1/3, 1/3)`