Ship Position
1. **State the problem:**
Town A is 30 km north of town B. A ship sails 25 km from town A on a bearing of 120°. We need to find how far east and south the ship is from town B.
2. **Understanding bearings:**
A bearing of 120° means the direction is measured clockwise from north. So, 120° is 30° east of due south (since 120° - 90° = 30°).
3. **Set up coordinate system:**
Let town B be at the origin $(0,0)$. Since town A is 30 km north of B, town A is at $(0,30)$.
4. **Calculate ship's displacement from A:**
The ship sails 25 km at 120° bearing from A.
- The angle from the positive x-axis (east) is $90° + 30° = 120°$.
- The east (x) component of the ship's displacement from A is:
$$x = 25 \times \sin(120^\circ) = 25 \times \frac{\sqrt{3}}{2} = 21.65 \text{ km}$$
- The north (y) component of the ship's displacement from A is:
$$y = 25 \times \cos(120^\circ) = 25 \times (-\frac{1}{2}) = -12.5 \text{ km}$$
5. **Find ship's coordinates relative to B:**
- East coordinate from B: $0 + 21.65 = 21.65$ km east
- North coordinate from B: $30 + (-12.5) = 17.5$ km north
6. **Find how far east and south the ship is from B:**
- East distance is $21.65$ km.
- Since the ship is still north of B by 17.5 km, the south distance from B is $0$ km.
**Final answer:**
The ship is approximately 21.65 km east and 0 km south of town B.