## Precalculus (6th Edition) Blitzer

Here, the wagon is pulled horizontally such that the angle between the force and direction of motion is $38{}^\circ$. Now, it is known that $\mathbf{W}=\left\| \mathbf{F} \right\|\left\| \mathbf{AB} \right\|\cos \theta$ …… (1) As it is given that $\left\| \mathbf{F} \right\|=25,\left\| \mathbf{AB} \right\|=100$ and $\theta =38{}^\circ$ …… (2) Therefore, use (2) in (1). So, \begin{align} & \mathbf{W}=\left( 25 \right)\left( 100 \right)\cos \left( 38{}^\circ \right) \\ & =\left( 2500 \right)\left( 0.788 \right) \\ & \approx 1970 \end{align}