Question : work, forces and vectors

Hi

If you are pulling a box along at a angle then the work performed is
W = cos(theta).F.d
where theta is the angle between the horizontal and F, F is the force applied along the angle and d is the displacement.

This can be written as W = F(dot) d and I'm not sure why. I presume F(dot)d is the dot product of F and d which is |F|.|d|.cos(theta). I thought the dot product was an operation performed on 2 vectors. I realise displacement is a vector but i thought theta was the angle between F and Fx, the horizontal component of F. I didn't see theta as the angle between the displacement vector and F.

Any comments welcomed.

Answer : work, forces and vectors

D                        Now pull a block up against a wall.
^
|
|
|
|     F                  Here, the angle between F and D is ß
|    ^                   F . D = |F| |D| cos ß
|ß /                     F and D are vectors
| /                      ß is the angle between the F and D
|/
---> Fx             In this case, D and Fx are NOT in the same direction
                       So, ß is NOT the angle between F and Fx
                       Now, F cos ß = Fy
                       So, ß is also the angle between F and Fy