## College Physics (4th Edition)

To travel straight across the river, the boat must be pointed upstream at an angle of $26.7^{\circ}$
In order to travel directly across the river, the upstream component of the boat's velocity relative to the water must be equal in magnitude to the water current of $1.8~km/h$. Let $\theta$ be the angle at which the boat is pointed upstream. We can find the angle $\theta$: $(4.0~km/h)~sin~\theta = 1.8~km/h$ $sin~\theta = \frac{1.8~km/h}{4.0~km/h}$ $\theta = sin^{-1}(\frac{1.8~km/h}{4.0~km/h})$ $\theta = 26.7^{\circ}$ To travel straight across the river, the boat must be pointed upstream at an angle of $26.7^{\circ}$