We now turn to the second theorem which speaks of an outwardly similar relationship between forces. As is well nown, this states that two forces of different magnitude and direction, when they apply at the same point, act together in the manner of a single force whose magnitude and direction may be represented by the diagonal of a parallelogram whose sides express in extent and direction the first two forces. Thus in Fig. 2, R exercises upon P the same effect as F₁ and F₂ together.