题目

Have you ever heard of the ancient Chinese story about Boya and Zhong Ziqi? On a rainy day, the famous guqin player, Boya, is sitting by the river. 【1】（quiet). Suddenly he sees a woodcutter 【2】 (call) Zhong Ziqi in the forest. Boya warmly invites Zhong Ziqi to come and listen【3】 his music.【4】 Boya plays his guqin and imagines tall mountains, Zhong Ziqi sees Mountain Tai reaching into 【5】 sky. When Boya thinks of rushing water, Zhong Ziqi says, Your music sounds like 【6】 (run) rivers! Whatever Boya thinks about, Zhong Ziqi hears in his music. They are 【7】（surpris如图，已知△ADE∽△ABC，AD=6cm，DB=3cm，BC=9.9cm，∠B=50°，则∠ADE= ，DE= cm．