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ICSE Class X Math 2013 Solved Paper

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In the figure given, from the top of a building AB=60m high, the angles of depression of the top and bottom of a vertical lamp post CD are observed to be 30∘ and 60∘ respectively. Find :
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Question : 30
Total: 46
The horizontal distance between AB and CD.
Solution:  
Given : AB=60m

‌∵‌‌∠P‌PAC=60∘
‌∴‌‌∠PAC=∠BCA
Now in △ABC ,
tan‌60∘‌=‌
AB
BC
√3‌=‌
60
BC
⇒‌‌BC‌=‌
60
√3
×‌
√3
√3
BC‌=‌
60√3
3
=20√3m
Hence, the horizontal distance between AB and CD=20√3m .
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