Question: A flagstaff 10 m long stands on top of a vertical tower. From a point on level ground, the angles of elevation of the top of the tower and the top of the flagstaff are 45° and 60° respectively. Find the exact height of the tower and its distance from the point. Also give the height to 2 decimal places.
1. **State the problem:**
We have a vertical tower with a flagstaff of length $10$ m on top. From a point on level ground, the angle of elevation to the top of the tower is $45^\circ$ and to the top of the flagstaff is $60^\circ$. We need to find the height of the tower and the horizontal distance from the point to the base of the tower.
2. **Define variables:**
Let the height of the tower be $h$ meters.
Let the horizontal distance from the point to the base of the tower be $d$ meters.
3. **Use trigonometric relations:**
- The angle of elevation to the top of the tower is $45^\circ$, so:
$$\tan 45^\circ = \frac{h}{d}$$
Since $\tan 45^\circ = 1$, we get:
$$1 = \frac{h}{d} \implies h = d$$
- The angle of elevation to the top of the flagstaff (which is $h + 10$ meters high) is $60^\circ$, so:
$$\tan 60^\circ = \frac{h + 10}{d}$$
Since $\tan 60^\circ = \sqrt{3}$, we get:
$$\sqrt{3} = \frac{h + 10}{d}$$
4. **Substitute $h = d$ into the second equation:**
$$\sqrt{3} = \frac{d + 10}{d} = 1 + \frac{10}{d}$$
5. **Solve for $d$:**
$$\sqrt{3} - 1 = \frac{10}{d}$$
$$d = \frac{10}{\sqrt{3} - 1}$$
6. **Rationalize the denominator:**
$$d = \frac{10}{\sqrt{3} - 1} \times \frac{\sqrt{3} + 1}{\sqrt{3} + 1} = \frac{10(\sqrt{3} + 1)}{(\sqrt{3})^2 - 1^2} = \frac{10(\sqrt{3} + 1)}{3 - 1} = \frac{10(\sqrt{3} + 1)}{2}$$
7. **Calculate exact height $h$:**
Since $h = d$, we have:
$$h = \frac{10(\sqrt{3} + 1)}{2}$$
8. **Calculate decimal approximations:**
$$\sqrt{3} \approx 1.732$$
$$h \approx \frac{10(1.732 + 1)}{2} = \frac{10(2.732)}{2} = 5 \times 2.732 = 13.66$$
So,
- Height of the tower $h \approx 13.66$ m
- Distance from the point $d \approx 13.66$ m
**Final answers:**
- Exact height of the tower: $$h = \frac{10(\sqrt{3} + 1)}{2}$$ meters
- Distance from the point: $$d = \frac{10(\sqrt{3} + 1)}{2}$$ meters
- Height to 2 decimal places: $13.66$ meters
- Distance to 2 decimal places: $13.66$ meters