When solving physics problems, it is often helpful to replace one force by a combination of two forces with given directions. Of course, these two forces must be equivalent to the given one. This means that their vector sum must agree with the given force. If this condition is fulfilled, we say that the force has been resolved into components. A simple geometrical construction provides the magnitudes of the components: We can draw two lines from the end of the given force vector parallel to the given directions. In this way, we get the so-called parallelogram of forces. The magnitudes of the components now can be read off from the sides of this parallelogram.