(1) Proof: From the next step △ AEM △ MCN? (ASA) The required conditions are verified as follows:

∠ 1=∠2.AE=MC，∠MCN =∠5；

(2) solution: true. Intercept a1h = m1c1on a1;

(3) Multiply ∠ AMN = 60 = (3? 2)3× 180，∠a 1m 1n 1 = 90 =(4？ 2)4× 180 ,

Guess: ∠ anmmnnn = (n? 2)n× 180。