On applying definite integral to find work done, we integrate F.dx and apply lower and upper limits. Should we apply the dot product, before integration , that is -1 for θ = 180, 1 for θ = 0. Or will the limits applied and their values suffice in deciding the sign of the final value. I have seen a famous lecture in which to find gravitational potential energy, on finding the work done in bringing a mass m from infinity to a point R , ∫F.dr is solved as ∫F*dr which actually should be a ∫-F*dr because applied force in that case is against gravitational attraction which must give cosθ as -1. The same confusion exists in case of finding out the electrostatic potential due to a positive charge. Kindly help me understand this.