1. **Problem statement:** We have two observation points 40 m apart on a straight line. From the first point, the angle of elevation to the top of the flagpole is 30° and from the second point, it is 45°. We need to find:
a) The height of the flagpole.
b) The distance from the first point to the base of the flagpole.
2. **Setup and notation:** Let the distance from the first point to the base of the flagpole be $x$ meters.
Then the distance from the second point to the base is $x - 40$ meters (since the points are 40 m apart).
Let the height of the flagpole be $h$ meters.
3. **Using trigonometry:** The tangent of the angle of elevation relates height and distance:
$$\tan(\theta) = \frac{h}{\text{distance}}$$
From the first point (angle 30°):
$$\tan(30^\circ) = \frac{h}{x}$$
From the second point (angle 45°):
$$\tan(45^\circ) = \frac{h}{x - 40}$$
4. **Values of tangent:**
$$\tan(30^\circ) = \frac{1}{\sqrt{3}}$$
$$\tan(45^\circ) = 1$$
5. **Write equations:**
From first point:
$$h = x \times \frac{1}{\sqrt{3}} = \frac{x}{\sqrt{3}}$$
From second point:
$$h = 1 \times (x - 40) = x - 40$$
6. **Equate the two expressions for $h$:**
$$\frac{x}{\sqrt{3}} = x - 40$$
7. **Solve for $x$:**
Multiply both sides by $\sqrt{3}$:
$$x = \sqrt{3}(x - 40) = \sqrt{3}x - 40\sqrt{3}$$
Rearrange:
$$x - \sqrt{3}x = -40\sqrt{3}$$
$$x(1 - \sqrt{3}) = -40\sqrt{3}$$
$$x = \frac{-40\sqrt{3}}{1 - \sqrt{3}}$$
Multiply numerator and denominator by the conjugate $(1 + \sqrt{3})$:
$$x = \frac{-40\sqrt{3}(1 + \sqrt{3})}{(1 - \sqrt{3})(1 + \sqrt{3})} = \frac{-40\sqrt{3} - 40 \times 3}{1 - 3} = \frac{-40\sqrt{3} - 120}{-2}$$
Simplify denominator:
$$x = \frac{-40\sqrt{3} - 120}{-2} = 20\sqrt{3} + 60$$
8. **Calculate numerical value:**
$$20\sqrt{3} \approx 20 \times 1.732 = 34.64$$
So,
$$x \approx 34.64 + 60 = 94.64 \text{ meters}$$
9. **Find height $h$:**
Using $h = \frac{x}{\sqrt{3}}$:
$$h = \frac{94.64}{1.732} \approx 54.6 \text{ meters}$$
10. **Final answers:**
a) Height of the flagpole $h \approx 54.6$ meters.
b) Distance from the first point to the base $x \approx 94.6$ meters.
Flagpole Height 18651A
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