As shown in Fig. 1, in RT △ ABC, ∠ ACB = 90 °, point 0 is the midpoint of BC, D is the upper moving point of AB, extend do to e, and OE = OD, connect CE (1) As shown in Figure 2, if D is the midpoint of AB, please judge the shape of quadrilateral EDAC and explain the reason; (2) as shown in Figure 3, if ∠ a = 60 ° and ∠ BOD = 30 °, is quadrilateral EDAC isosceles trapezoid? Please explain the reason; (3) if AC = 15, ab = 25, please make the location of point D in Figure 4 to minimize the perimeter of the quadrilateral EDAC, please complete the figure and find out the minimum perimeter of the quadrilateral EDAC

As shown in Fig. 1, in RT △ ABC, ∠ ACB = 90 °, point 0 is the midpoint of BC, D is the upper moving point of AB, extend do to e, and OE = OD, connect CE (1) As shown in Figure 2, if D is the midpoint of AB, please judge the shape of quadrilateral EDAC and explain the reason; (2) as shown in Figure 3, if ∠ a = 60 ° and ∠ BOD = 30 °, is quadrilateral EDAC isosceles trapezoid? Please explain the reason; (3) if AC = 15, ab = 25, please make the location of point D in Figure 4 to minimize the perimeter of the quadrilateral EDAC, please complete the figure and find out the minimum perimeter of the quadrilateral EDAC

(1) Point 0 is the middle point of BC, that is, OC = ob, OE = OD, ∠ EOC = ∠ DOB, ≌ COE ≌ △ BOD. ≌ CE = dB, ≌ e = ∠ EDB, ∥ CE ∥ AB, and D is the middle point of AB, ∥ CE = ad. according to the parallelogram discriminant theorem, EDAC is a parallelogram. (2) from (1), it can be seen that CE ∥ AB, ≌ quadrilateral EDAC is a trapezoid. In RT △ ABC, ∥ a = 60 °, and ∥ B = 30 °, and ∥ BOD = 30 ° and ∥ (3) according to figures 1, 2 and 3, CE and BD have the same length, so only when Ed is the minimum, the perimeter of quadrilateral EDAC will be the minimum, so only when Ed ⊥ AB, the perimeter of quadrilateral EDAC will be the minimum. For RT ⊥ ABC, BC = 20, ∫ Bo = 10 ∫ B = ∫ OCE, ∫ ODB = ∫ e = 90 ° and ∽ BOD ∽ BAC can be obtained by Pythagorean theorem The results show that, the circumference of the quadrilateral EDAC is 15 + 25 + 12 = 52