Answers

2016-01-28T20:43:50+05:30
AB- building 100m 
angle of dep. 30'
Car at C
angle ACB +30' (alternate angles)
tan 30 +1/root(3) = AB/BC= 100/BC
BC =100*root(3)
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2016-01-28T20:46:26+05:30
Given here, Angle of depression=30 degrees.
Height of tower = 100 m
It will make a triangle if you take an point to represent car.
Rotate your figure to left side.
30 degrees will shift to down & 100m will be base.
let the distance between building and car be x m.
therefore 
tan 30 degrees=x m/100m
Simply it, you will get 57.74 m as the answer.
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thank-you brother
You are welcome, Hope this helped you.......