An airplane is at a horizontal distance of 1050 m from a control tower. The angles of depression from the airplane to the top and base of the tower are $36^\circ$ and $41^\circ$ respectively. We need to calculate the height of the control tower and the shortest distance between the airplane and the base of the control tower.

GeometryTrigonometryAngles of DepressionRight TrianglesPythagorean Theorem
2025/4/21

1. Problem Description

An airplane is at a horizontal distance of 1050 m from a control tower. The angles of depression from the airplane to the top and base of the tower are 3636^\circ and 4141^\circ respectively. We need to calculate the height of the control tower and the shortest distance between the airplane and the base of the control tower.

2. Solution Steps

Let hh be the height of the control tower, and xx be the vertical distance from the airplane to the top of the tower. Let dd be the horizontal distance from the airplane to the tower, which is given as 1050 m.
Let θ1\theta_1 be the angle of depression to the top of the tower, and θ2\theta_2 be the angle of depression to the base of the tower. We are given that θ1=36\theta_1 = 36^\circ and θ2=41\theta_2 = 41^\circ.
The vertical distance from the airplane to the base of the tower is x+hx+h.
We can use the tangent function to relate the angles of depression to the distances:
tan(θ1)=xdtan(\theta_1) = \frac{x}{d}, so tan(36)=x1050tan(36^\circ) = \frac{x}{1050}.
tan(θ2)=x+hdtan(\theta_2) = \frac{x+h}{d}, so tan(41)=x+h1050tan(41^\circ) = \frac{x+h}{1050}.
First, we find xx:
x=1050tan(36)=10500.7265762.825x = 1050 \cdot tan(36^\circ) = 1050 \cdot 0.7265 \approx 762.825
Next, we find x+hx+h:
x+h=1050tan(41)=10500.8693912.765x+h = 1050 \cdot tan(41^\circ) = 1050 \cdot 0.8693 \approx 912.765
Now, we can find hh:
h=(x+h)x=912.765762.825=149.94h = (x+h) - x = 912.765 - 762.825 = 149.94
So, the height of the tower is approximately 150 m.
For the shortest distance between the airplane and the base of the control tower, we can use the Pythagorean theorem or the cosine function. Let DD be this distance. We have:
cos(θ2)=dDcos(\theta_2) = \frac{d}{D}
D=dcos(θ2)=1050cos(41)=10500.75471391.28D = \frac{d}{cos(\theta_2)} = \frac{1050}{cos(41^\circ)} = \frac{1050}{0.7547} \approx 1391.28
Alternatively, we can use the Pythagorean theorem:
D=d2+(x+h)2=10502+912.7652=1102500+833180.5=1935680.51391.29D = \sqrt{d^2 + (x+h)^2} = \sqrt{1050^2 + 912.765^2} = \sqrt{1102500 + 833180.5} = \sqrt{1935680.5} \approx 1391.29
So, the shortest distance between the airplane and the base of the control tower is approximately 1391 m.

3. Final Answer

(i) The height of the control tower is 150 m.
(ii) The shortest distance between the airplane and the base of the control tower is 1391 m.

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