So that means we take the cosine of the angle. If you want to learn more about dot product and cross product, check out the lecture on that. So, basically, if we have some object, say, this block, and we apply a force with an angle theta to the horizontal of that object, and our object moves a distance d we can find the amount of work done on the object. The amount of energy that object gain by using the following formula force times, distance travel times, cosine of the angle between them. Now, if we do not neglect friction, if we actually include friction, for example, when this box is traveling along this horizontal surface, there is friction in a real world situation. So if we do not neglect friction, we find our overall work by following the following formula the work done is equal to change in our potential energy of the object plus change in the kinetic energy of the object plus the change in the internal energy of our object due to friction.