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A 1.5m tall boy stands at a distance of 3m from a lamp post and casts a shadow of 4.5m on the ground.find the height of lamp post by trignometric ratios



Let AB be boy = 1.5m
CD be lamp = Let it be x m.
OB be shadow cast by boy = 4.5m
BD be distance between boy and lamp = 3m

=> tan θ = AB/OB
=> tan θ = CD/OD = CD/(OB+BD)

∴ AB/OB = CD/(OB+BD)
=> 1.5/4.5 = CD/(4.5+3)
=> CD = 7.5/3 = 2.5m
2 2 2
See diagram for details on this problem.
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