On the top of the fake mountain, the reflection angle of the roof in the lake is 45. According to the fact that the two right angles of the isosceles right triangle are equal, it is concluded that
h+4=√3(h-4)
The solution is h = 4 (√ 3+1)/(√ 3-1) = 2 (4+2 √ 3) = 4 (2+√ 3) √14.928 (m).
The height of the library is (14.928) meters.
I don't understand. Need to get the right picture.