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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 :
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- 60 √3
- 30 ( √3 - 1 )
- 30 ( √3 + 1 )
- 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 + 60 | √3 |
∴ MP + 60 | = | √3h or, h + 60 = √3h |
∴ ( √3 - 1 )h = 60 |
∴ | h = | 60 | h = | 60 ( √3 + 1 ) | 30 ( √3 + 1 ) m |
√3 - 1 | 2 |