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Two towers of the same height stand on o...

Two towers of the same height stand on opposite sides of a road 100 m wide. At a point on the road between the towers. The elevations of the towers are `30^(@) and 45^(@)`. Find the height of the towers and the position of the point from the nearest tower :

A

36.6 m and 63.4 m

B

63.3 m and 63.4 m

C

66.3 m and 63.4 m

D

36.6 m and 86. 4m

Text Solution

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The correct Answer is:
To solve the problem, we will use trigonometric ratios to find the height of the towers and the position of the point from the nearest tower. ### Step 1: Define the problem Let the height of the towers be \( h \). Let the distance from the point on the road to the nearest tower (the tower with a \( 30^\circ \) elevation) be \( x \). Therefore, the distance to the other tower (with a \( 45^\circ \) elevation) will be \( 100 - x \). ### Step 2: Set up the equations using trigonometry Using the tangent function, we can set up the following equations based on the angles of elevation: 1. For the tower with a \( 30^\circ \) elevation: \[ \tan(30^\circ) = \frac{h}{x} \] We know that \( \tan(30^\circ) = \frac{1}{\sqrt{3}} \), so: \[ \frac{1}{\sqrt{3}} = \frac{h}{x} \quad \Rightarrow \quad h = \frac{x}{\sqrt{3}} \quad \text{(Equation 1)} \] 2. For the tower with a \( 45^\circ \) elevation: \[ \tan(45^\circ) = \frac{h}{100 - x} \] Since \( \tan(45^\circ) = 1 \), we have: \[ 1 = \frac{h}{100 - x} \quad \Rightarrow \quad h = 100 - x \quad \text{(Equation 2)} \] ### Step 3: Equate the two expressions for height From Equation 1 and Equation 2, we can set them equal to each other: \[ \frac{x}{\sqrt{3}} = 100 - x \] ### Step 4: Solve for \( x \) To solve for \( x \), first multiply both sides by \( \sqrt{3} \): \[ x = \sqrt{3}(100 - x) \] Expanding this gives: \[ x = 100\sqrt{3} - \sqrt{3}x \] Now, add \( \sqrt{3}x \) to both sides: \[ x + \sqrt{3}x = 100\sqrt{3} \] Factor out \( x \): \[ x(1 + \sqrt{3}) = 100\sqrt{3} \] Now, divide both sides by \( (1 + \sqrt{3}) \): \[ x = \frac{100\sqrt{3}}{1 + \sqrt{3}} \] ### Step 5: Calculate \( h \) Now that we have \( x \), we can substitute it back into either Equation 1 or Equation 2 to find \( h \). Using Equation 2: \[ h = 100 - x = 100 - \frac{100\sqrt{3}}{1 + \sqrt{3}} \] To simplify this, we can find a common denominator: \[ h = \frac{(100 + 100\sqrt{3}) - 100\sqrt{3}}{1 + \sqrt{3}} = \frac{100}{1 + \sqrt{3}} \] ### Step 6: Final results Now we have \( x \) and \( h \): 1. The height of the towers \( h = \frac{100}{1 + \sqrt{3}} \). 2. The distance from the nearest tower \( x = \frac{100\sqrt{3}}{1 + \sqrt{3}} \).
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Knowledge Check

  • At a point 20 m away from the foot of a tower the angle of elevation of the top of the tower is 30^(@) The height of the tower is

    A
    `20sqrt3m`
    B
    `(20)/(sqrt3)m`
    C
    `(sqrt3)/(20)m`
    D
    None of these
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    A
    `20 sqrt(3) m`
    B
    `(20)/(sqrt(3))m`
    C
    `(sqrt(3))/(20m )`
    D
    None of these
  • From a point 20 m away from the foot of a tower, the angle of elevation of the top of the tower is 30^(@) . The height of the tower is

    A
    ` 10 sqrt(3) m`
    B
    `20 sqrt(3)` m
    C
    `10/sqrt(3)` m
    D
    `(20)/(sqrt(3))m`
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