A block of weight W W\,W is held in equilibrium on a smooth inclined plane of angle α \alpha\,α to the horizontal. A pulling force of magnitude P P\,P is applied to the block at an angle β \beta\,β above the inclined plane, as shown in the diagram below. The normal reaction force exerted by the plane on the block is RRR.
Which of the following expressions correctly gives the magnitude of the normal reaction force RRR?
R=Wcosα+PsinβR = W \cos \alpha + P \sin \betaR=Wcosα+Psinβ
R=Wsinα−PcosβR = W \sin \alpha - P \cos \betaR=Wsinα−Pcosβ
R=Wcosα−PsinβR = W \cos \alpha - P \sin \betaR=Wcosα−Psinβ
R=Wsinα−PsinβR = W \sin \alpha - P \sin \betaR=Wsinα−Psinβ