The vectors a and b represent two forces acting at the same point, and $\theta$ is the smallest positive angle between a and b. Approximate the magnitude of the resultant force.
$$|\mathbf{a}|=5.5 \mathrm{Ib}, \quad\|\mathbf{b}\|=6.2 \mathrm{Ib}, \quad \theta=60^{\circ}$$