Reference: Edexcel C4 book, Mixed Ex 5K Q10 part (d).I have named a point C on the line, where BC is the perpendicular distance from B to the line. I have called C's coordinates (x, y, z). So, the vector BC (x-10, y+2, z-2) dotted with the directional vector of the line (3, -1, 1) must equal 0 (because they're perpendicular). When I worked this out, I found x=10, y=-2 and z=2. For some reason this gave me position vector of B, not the position vector of C. Can anyone tell me what I've done wrong?