F. 4 maths - 三角學 高手請進

well... i'm not exactly sure about where point B is but i assume it is the point where A and the 涼亭底部 is the closest.

so, firstly consider '18ﾟ的山坡上', the first thing is to find the distance form 涼亭 and A horizontal to 水平地面 which is 20cos18.

then consider the height of 涼亭, it will be
(20cos18)*tan(48) -------- the height of (涼亭&山坡 above A) minus
(20cos18)*tan(18) -------- the height of 山坡 above A
=> (20cos18)*tan(48) - (20cos18)*tan(18) = 14.9(4)m

The last sentence does not state the question clearly.