तीन समतलीय सदिश P, Q तथा R किसी बिन्दु पर

$\frac{P}{{\sin {\theta _1}}} = \frac{Q}{{\sin {\theta _2}}} = \frac{R}{{\sin \,\,150^\circ }}$

$ \Rightarrow \,\frac{{1.93}}{{\sin {\theta _1}}} = \frac{R}{{\sin \,150^\circ }}$

$ \Rightarrow \,R = \frac{{1.93 \times \sin \,150^\circ }}{{\sin {\theta _1}}} = \frac{{1.93 \times 0.5}}{{0.9659}} = 1$