Pole Heights
1. **State the problem:**
Two poles stand opposite each other across a road 80 m wide.
One pole's height is \( \frac{3}{4} \) of the other's.
From a certain point between them on the road, the angles of elevation to the tops of the poles are 60° and 30°.
Find the heights of both poles and the distances from that point to each pole.
2. **Assign variables:**
Let the height of the taller pole be \( H \).
Then the shorter pole's height is \( \frac{3}{4}H \).
Let the distance from the point on the road to the taller pole be \( x \).
Then the distance to the shorter pole is \( 80 - x \).
3. **Use tangent of angles of elevation:**
From the point, the angle of elevation to the taller pole's top is 60°, so
$$ \tan 60^\circ = \frac{\text{height of taller pole}}{\text{distance to taller pole}} = \frac{H}{x} $$
And the angle to the shorter pole is 30°, so
$$ \tan 30^\circ = \frac{\frac{3}{4}H}{80 - x} $$
4. **Recall tangent values:**
$$ \tan 60^\circ = \sqrt{3} $$
$$ \tan 30^\circ = \frac{1}{\sqrt{3}} $$
5. **Write equations:**
$$ \sqrt{3} = \frac{H}{x} \implies H = x \sqrt{3} $$
$$ \frac{1}{\sqrt{3}} = \frac{\frac{3}{4}H}{80 - x} \implies \frac{1}{\sqrt{3}} = \frac{3H}{4(80 - x)} $$
6. **Substitute \( H = x \sqrt{3} \) into second equation:**
$$ \frac{1}{\sqrt{3}} = \frac{3 (x \sqrt{3})}{4(80 - x)} = \frac{3x\sqrt{3}}{4(80 - x)} $$
7. **Multiply both sides by denominator:**
$$ (80 - x) \times \frac{1}{\sqrt{3}} = \frac{3x\sqrt{3}}{4} $$
8. **Multiply both sides by \( 4 \sqrt{3} \):**
$$ 4 \sqrt{3} (80 - x) \times \frac{1}{\sqrt{3}} = 4 \sqrt{3} \times \frac{3x \sqrt{3}}{4} $$
Simplifies to
$$ 4 (80 - x) = 3x \times 3 $$
$$ 320 - 4x = 9x $$
9. **Solve for \( x \):**
$$ 320 = 9x + 4x = 13x $$
$$ x = \frac{320}{13} \approx 24.62 \, \text{m} $$
10. **Find the height \( H \):**
$$ H = x \sqrt{3} = \frac{320}{13} \times 1.732 \approx 42.68 \, \text{m} $$
11. **Find shorter pole's height:**
$$ \frac{3}{4} H = \frac{3}{4} \times 42.68 \approx 32.01 \, \text{m} $$
12. **Find distance from point to shorter pole:**
$$ 80 - x = 80 - 24.62 = 55.38 \, \text{m} $$
**Final answers:**
- Taller pole height: approximately \( 42.68 \) m
- Shorter pole height: approximately \( 32.01 \) m
- Distance from point to taller pole: approximately \( 24.62 \) m
- Distance from point to shorter pole: approximately \( 55.38 \) m