## Trigonometry (11th Edition) Clone

Let $a = 18~lb$ Let $b = 12~lb$ Let angle $\theta$ be the angle between these two forces. Then $\theta = 10^{\circ}+15^{\circ}= 25^{\circ}$ We can use the parallelogram rule to find $c$, the magnitude of the resultant force: $c = \sqrt{a^2+b^2+2ab~cos~\theta}$ $c = \sqrt{(18~lb)^2+(12~lb)^2+(2)(18~lb)(12~lb)~cos~25^{\circ}}$ $c = \sqrt{859.5~lb^2}$ $c = 29~lb$ The magnitude of the resultant force is 29 lb