
Answer: 335ft
Step-by-step explanation:
The tangent of the angle of elevation is the ratio of the dam height h to the horizontal distance downriver of the observer. This gives us two equations for the height:
h= atan(1.1) = (155+a) tan(0.8)
âıa= h/tan(1.3), 155+a= h/tan(0.8).
Subtracting the first equation from the second,
155=(155+a)âa =h/tan(0.8)âh/tan(1.1)
=h(1/tan(0.8)â1/tan(1.1)).
Solving for h,
h=155 ft (1tan(0.8)â1tan(1.1))â1
155(0.9713 - 0.5090)^-1
155(2.1631) â335 ft .