And so, the unit vector we'll give the symbol e.

From D to C, and if you recall back to that earlier course, you

want to walk from the tail of that vector to the head of the vector.

And so we're going to find the position vector from D to C, and then divide

it by the magnitude of that position vector, in

order to find the unit vector in that direction.

So, in going from D to C.

We have to go 3 units in the negative x direction, 4 units in the

negative y direction and 12 units in the positive z direction.

So we are going to have minus 3i minus 4j plus

12k over the magnitude of that vector that

position vector which is the square root of the

sum of the squares which in this case ends up being

13. And then FDC.

The force expressed as a vector is equal to the magnitude

of the force, times it's direction. We just found the direction to

be the unit vector eDC. And so, we have