What is the distance from the point (1, 8, 1) to the xz-plane? Solution the equation of the xz plane is y = 0, but you don\'t need it. n = <0,1,0> is the unit normal to the x-z plane v = <0,8,0> .... is an arbitrary vector from the x-z plane to (1,8,1) the minimum point-plane distance is the magnitude of the projection of v on n: d = |v·n| = 8 Answer: 8.