As the picture shows, AC is the height of a building in our city. The elevation of roof A measured at point B on the ground is 45, and it reaches point D along BC direction 18m, and tan∠AD is measured

As the picture shows, AC is the height of a building in our city. The elevation of roof A measured at point B on the ground is 45, and it reaches point D along BC direction 18m, and tan∠AD is measured. Solution: In Rt△ABC, ∠ ACB = 90, ∠ ABC = 45,

∴Rt△ABC is an isosceles right triangle, AC=BC,

In Rt△ADC, ∠ ACD = 90,

∴ ,

∫BC-DC = BD, namely AC- AC= 18,

∴AC=45，

AE=AC-EC=45- 15=30，

A: AE slogan should be 30 meters long.