Plane Distance Bearing 989Df3
1. **Problem statement:** An airplane leaves Manila and flies 300 km on a bearing N 55° W, then flies 200 km on a bearing S 25° W. We need to find the distance from Manila after the second leg and the bearing from Manila.
2. **Understanding bearings:**
- Bearing N 55° W means starting north and turning 55° towards the west.
- Bearing S 25° W means starting south and turning 25° towards the west.
3. **Convert bearings to standard angles:**
- N 55° W corresponds to an angle of 360° - 55° = 305° from the east counterclockwise.
- S 25° W corresponds to 180° + 25° = 205°.
4. **Calculate components of each leg:**
For leg 1 (300 km, 305°):
$$x_1 = 300 \cos 305^\circ = 300 \cos (360^\circ - 55^\circ) = 300 \cos 55^\circ \approx 300 \times 0.5736 = 172.08$$
$$y_1 = 300 \sin 305^\circ = 300 \sin (360^\circ - 55^\circ) = 300 (-\sin 55^\circ) \approx 300 \times (-0.8192) = -245.76$$
For leg 2 (200 km, 205°):
$$x_2 = 200 \cos 205^\circ = 200 \cos (180^\circ + 25^\circ) = 200 (-\cos 25^\circ) \approx 200 \times (-0.9063) = -181.26$$
$$y_2 = 200 \sin 205^\circ = 200 \sin (180^\circ + 25^\circ) = 200 (-\sin 25^\circ) \approx 200 \times (-0.4226) = -84.52$$
5. **Sum components to find resultant vector:**
$$x = x_1 + x_2 = 172.08 - 181.26 = -9.18$$
$$y = y_1 + y_2 = -245.76 - 84.52 = -330.28$$
6. **Calculate distance from Manila:**
$$d = \sqrt{x^2 + y^2} = \sqrt{(-9.18)^2 + (-330.28)^2} = \sqrt{84.27 + 109084.58} = \sqrt{109168.85} \approx 330.5 \text{ km}$$
7. **Calculate bearing from Manila:**
- Find angle $\theta$ from east axis:
$$\theta = \arctan \left( \frac{y}{x} \right) = \arctan \left( \frac{-330.28}{-9.18} \right) = \arctan(35.97) \approx 88.4^\circ$$
- Since $x<0$ and $y<0$, the vector is in the third quadrant.
- Bearing is measured clockwise from north, so:
$$\text{Bearing} = 180^\circ + (90^\circ - 88.4^\circ) = 180^\circ + 1.6^\circ = 181.6^\circ$$
- Convert to compass bearing:
Since the vector points slightly west of south, bearing is S 1.6° W.
**Final answers:**
- Distance from Manila after second leg is approximately **330.5 km**.
- Bearing from Manila is approximately **S 1.6° W**.