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From the top of a hill, the angles of de...

From the top of a hill, the angles of depression of two consecutive kilometre stones, due east, are found to be `30^(@) and 45^(@)` respectively. Find the distance of the two from the foot of the hill

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To solve the problem step by step, we will use trigonometric principles and the properties of right triangles. ### Step-by-Step Solution: 1. **Draw the Diagram**: - Let the height of the hill be \( AB = h \). - Let \( C \) be the position of the first kilometer stone (at an angle of depression of \( 30^\circ \)). - Let \( D \) be the position of the second kilometer stone (at an angle of depression of \( 45^\circ \)). - The distance from the foot of the hill to stone \( C \) is \( x \) kilometers, and the distance to stone \( D \) is \( x + 1 \) kilometers (since the stones are consecutive). 2. **Use the Angle of Depression**: - For angle \( 45^\circ \) (stone \( D \)): \[ \tan(45^\circ) = \frac{h}{x} \] Since \( \tan(45^\circ) = 1 \): \[ h = x \quad \text{(Equation 1)} \] - For angle \( 30^\circ \) (stone \( C \)): \[ \tan(30^\circ) = \frac{h}{x + 1} \] Since \( \tan(30^\circ) = \frac{1}{\sqrt{3}} \): \[ \frac{1}{\sqrt{3}} = \frac{h}{x + 1} \] Cross-multiplying gives: \[ h \sqrt{3} = x + 1 \quad \text{(Equation 2)} \] 3. **Substitute Equation 1 into Equation 2**: - Substitute \( h = x \) into Equation 2: \[ x \sqrt{3} = x + 1 \] - Rearranging gives: \[ x \sqrt{3} - x = 1 \] \[ x(\sqrt{3} - 1) = 1 \] \[ x = \frac{1}{\sqrt{3} - 1} \] 4. **Rationalize the Denominator**: - Multiply the numerator and denominator by the conjugate \( \sqrt{3} + 1 \): \[ x = \frac{1(\sqrt{3} + 1)}{(\sqrt{3} - 1)(\sqrt{3} + 1)} = \frac{\sqrt{3} + 1}{3 - 1} = \frac{\sqrt{3} + 1}{2} \] 5. **Calculate the Value of \( x \)**: - Now, substituting the value of \( \sqrt{3} \approx 1.732 \): \[ x = \frac{1.732 + 1}{2} = \frac{2.732}{2} \approx 1.366 \text{ kilometers} \] 6. **Find the Distance to the Second Stone**: - The distance to stone \( D \) is: \[ x + 1 = 1.366 + 1 = 2.366 \text{ kilometers} \] ### Final Answers: - Distance to the first stone \( C \): \( 1.366 \) kilometers - Distance to the second stone \( D \): \( 2.366 \) kilometers
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ICSE-HEIGHTS AND DISTANCES -Exercise 22 B
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  4. From the top of a light house 100 m high, t he angles of depression of...

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  7. From the figure, given below . calculate the length of CD

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  8. The angle of elevation of the top of a tower is observed to be 60^(@) ...

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  9. The angle of elevation of the top of a tower is observed to be 60^(@) ...

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  11. A man on a cliff observes a boat, at an angle of depression 30^(@) , w...

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  12. A man on a cliff observes a boat, at an angle of depression 30^(@) , w...

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  13. A man in a boat rowing away from a lighthouse 150 m high, takes2 minut...

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  15. A person standing on the bank of a river observes that the angle of ...

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  16. The horizontal distance between two towers is 75 m and the angular de...

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  17. The length of the shadow of a tower standing of level plane is found ...

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