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Answer:
Height of the lamppost = 5.602 ft + 2.912 ft = 8.514 ft
Step-by-step explanation:
The illustration form a triangle that can be demarcated into 2 right angle triangle. One triangle representing depression triangle and the other elevation triangle.
Depression triangle
The opposite side of the triangle formed is the length of the pole from the base to the horizontal line of sight. Therefore,
using tangential ratio
tan 35° = opposite/adjacent
tan 35° = a/8
cross multiply
a = 8 tan 35°
a = 8 × 0.70020753821
a = 5.60166030568
a = 5.602 ft
Elevation triangle
The opposite side of this right angle triangle represent the length from the horizontal line of sight to the top of the lamppost.
tan 20° = opposite/adjacent
tan 20° = b/8
cross multiply
b = 8 tan 20°
b = 8 × 0.36397023426
b = 2.91176187413
b = 2.912 ft
Height of the lamppost = 5.602 ft + 2.912 ft = 8.514 ft
He should buy two 5 pound bags and one 2 pound bag.
