Originally Posted by

**free_to_fly** Q: What are the properties of the plane $\displaystyle \

b.(r - a) = 0

\$?

If O is the origin and a point C has position vector c, find:

a) the length of the projection of OC onto the plane

b) the distance of C from the plane.

For part a) this sound like it has something to do with the scalar product?

For part b) I know how to find the distance of a point to a plane using the formula:

$\displaystyle \

d = \left| {\frac{{n_1 a + n_2 b + n_3 c + d}}{{\sqrt {n_1^2 + n_2^2 + n_3^2 } }}} \right|

\$

Help would be hugely appreciated.