1. **State the problem:** A lighthouse is 25 meters above sea level. The angle of depression to a sailboat at sea level is 10°. We need to find the horizontal distance from the base of the lighthouse to the sailboat. 2. **Identify the right triangle and trigonometric function:** The height of the lighthouse is the opposite side to the angle of depression, and the horizontal distance to the sailboat is the adjacent side. 3. **Use the tangent function:** $$\tan(\theta) = \frac{\text{opposite}}{\text{adjacent}}$$ Here, $\theta = 10^\circ$, opposite = 25 meters, adjacent = distance $d$. 4. **Set up the equation:** $$\tan(10^\circ) = \frac{25}{d}$$ 5. **Solve for $d$:** $$d = \frac{25}{\tan(10^\circ)}$$ 6. **Calculate $\tan(10^\circ)$:** $$\tan(10^\circ) \approx 0.1763$$ 7. **Substitute and compute:** $$d = \frac{25}{0.1763} \approx 141.8$$ 8. **Answer:** The sailboat is approximately **141.8 meters** from the base of the lighthouse.