Distance of point Pp→ from the plane r→.n→ is

Let Q(q→). the foot of altitude drawn from P to the plane r→.n→=0 Thenq→−p→=λn→  or q→=p→+λn→also  q→⋅n→=0⇒(p→+λn→)⋅n→=0or  λ=−p→⋅n→|n→|2 or q→−p→=−(p→⋅n→)|n→|2n→Thus, required distance =|q→−p→|=|p→⋅n→||n→|=|p→⋅n^|