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    Question

    The angle of elevation of the top of a building from a point on the ground is 60°. After walking 20 meters towards the building, the angle of elevation becomes 75°. Find the initial distance from the point on the ground to the building.

    A 10(√3-1) meters Correct Answer Incorrect Answer
    B 10(√3+1) meters Correct Answer Incorrect Answer
    C 10(√3+2) meters Correct Answer Incorrect Answer
    D 10(√3-2) meters Correct Answer Incorrect Answer

    Solution

    Let the height of the building be h meters, and the initial distance from the point on the ground to the building be d. From the first observation: tan(60°) = h/d, so h = d√3. From the second observation: tan(75°) = h/(d - 20). 2+√3= d√3/(d - 20)  d = 10(√3+2) meters. Correct option: c

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