(20 1 1? Urumqi) An extracurricular activity group of a school, at the observation station A 7 meters away from the lake, looks at the elevation angle of the hot air balloon P over the lake at 37. Loo

(20 1 1? Urumqi) An extracurricular activity group of a school, at the observation station A 7 meters away from the lake, looks at the elevation angle of the hot air balloon P over the lake at 37. Look at that. Solution: If point A is AD⊥PP' and vertical foot is D, then CD = AB = 7m.

Let PC be x meters, then P ′ c = x meters, PD=(x-7) meters, P ′ d = (x+7) meters,

In Rt△PDA, ad = pdtan 37 ≈ 43 (x-7).

In rt △ p ′ da, ad = p ′ dtan53 ≈ 34 (x+7),

∴43(x-7)=34(x+7)，

Solution: x = 25.

A: The height PC of hot air balloon P from the lake is about 25 meters.