8. (There are 3 small questions in this question, and the first small question is required; Questions 2 and 3 are entitled optional answers, of which, questions 2 have full marks and questions 3 have full marks. Please select 1 questions to answer. If you answered two questions, grade question 2. )

At △ABC, ∠ ACB = 90, AC=BC, straight line MN passes through point C, AD⊥MN is in D, BE⊥MN is in E.

①(6 points) When the straight line MN rotates around point C to the position of 1, verify that:

⑴△ADC?△CEB； ⑵DE = AD+BE；

②(4 points) When the straight line MN rotates around point C to the position in Figure 2, it is proved that DE = AD-BE;

③(5 points) When the straight line MN rotates around point C to the position in Figure 3, what is the equivalent relationship among DE, AD and BE? Please write this equivalence relation and prove it.

Note: The second and third questions you choose to answer are the first question.

9. (Wuxi, 2004, 12) It is known that T > in Rt△ABC, ∠ B = 90, ∠ A = 30, BC=6㎝. Point O starts from point A and moves along AB at a speed of ÷ per second to point B. 0). The circle centered on point O is tangent to point D with AC edge, and intersects with AB edge at two points E and F. The intersection E makes the intersection BC of EG⊥DE at g.

(1) If E and B do not coincide, when asked what the value of T is, are △BEG and △DEG similar?

(2) Q: When T is in what range, is the G point on the BC line? When t is in what range, the G point is on the extension line of BC line?

(3) When the G point is on the BC line (excluding the endpoints B and C), find the functional relationship between the area S(㎝2) of the quadrilateral CDEG and the time t (seconds), and find the maximum value of S when the O point moves for several seconds. What is the maximum value?