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  1. Angle of depression from the top of a lighthouse of two boats are 45° and 30° due east which are 60 m apart. The height of the light house is :
    1. 60 √3
    2. 30 ( √3 - 1 )
    3. 30 ( √3 + 1 )
    4. None of these
Correct Option: C

As per given figure , we have
Let, the boats be at P, Q. So that PQ = 60m. Let, MA be the lighthouse.
Let, h = MA.

Then,h = tan45° = 1. ∴ h = MP
MP

Again,h = tan30° = 1
MP + 603

∴ MP + 60 = 3h or, h + 60 = √3h

∴ ( √3 - 1 )h = 60

h = 60 h = 60 ( √3 + 1 ) 30 ( √3 + 1 ) m
3 - 12



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