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  1. A helicopter, at an altitude of 1500 metre, finds that two ships are sailing towards it, in the same direction. The angles of depression of the ships as observed from the helicopter are 60° and 30° respectively. Distance between the two ships, in metre is
    1. 1000
      3
    2. 1000 √3
    3. 500 √3
    4. 500
      3
Correct Option: A


AD = Height of helicopter = 1500 metre
C and D ⇒ positions of ships
∠ADB = 30°; ∠ACB = 60°
Let, BC = x metre and BD = y metre
In ∆ABD,

tan 30° =
AB
BD

1
=
1500
3y

⇒ y = 1500 √3 metre ...(i)
In ∆ABC,
tan 60° =
AB
BC

⇒√3
=
1500
x

⇒x =
1500
3

= 500 √3 metre ...(ii)
∴ Distance between ships
= (y – x) metre
= (1500 √3 500 √3 - ) metre
= 1000 √3 metre



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