The distance from the point P to the plane p is the shortest distance between P and a point in p, and is equal to |PN|, where N is the point in p such that the line PN is normal to p. If P has coordinates (x1, y1, z1) and p has equation ax + by + cz + d = 0, the distance from P to p is equal to
where |ax1 + by1 + cz1 + d| is the absolute value of ax1 + by1 + cz1 + d.