In the free-body diagram in Fig. 6.4b, the incremental stress dx on the element was shown pointing

In the free-body diagram in Fig. 6.4b, the incremental stress dσx on the element was shown pointing to the left. Yet it would appear that, because of the direction of frictional stresses, μp, the incremental stress should point to the right in order to balance the horizontal forces. Show that the same answer for the forging pressure is obtained regardless of the direction of this incremental stress.