In the general case suppose that the radial forces are of magnitude P and that the angle between adjacent forces is 2α (so that α = 20° in the above figure). Consider the portion YY′ of the ring, as in the left-hand figure below. From a consideration of the rotational symmetry of the ring, it is evident that the tensions at Yand Y′are equal, these being marked T in the figure. Similarly, if the shear force at Y is Stowards the centre O, then that at Y′ is S away from the centre. Moreover, the bending moments at Y and Y′ are equal and opposite. These are marked M in the left-hand figure.