(1) As shown in the figure, the triangle ABC paper is folded along De to form figure 1. At this time, point a falls inside the quadrilateral bced, and there is a quantitative relationship between angle A and angle 1 and angle 2, which remains unchanged. Find out the quantitative relationship and explain the reason; (2) If the point a falls on be or CD, write the relationship between angle A and angle 2, angle A and angle 1, and explain the reason; (3) If folded into Figure 4, write the relationship between angle A and angle 1, angle 2, and explain the reason; (3) if folded into figure 5, write the relationship between angle A and angle 1, angle 2, and explain the reason

(1) As shown in the figure, the triangle ABC paper is folded along De to form figure 1. At this time, point a falls inside the quadrilateral bced, and there is a quantitative relationship between angle A and angle 1 and angle 2, which remains unchanged. Find out the quantitative relationship and explain the reason; (2) If the point a falls on be or CD, write the relationship between angle A and angle 2, angle A and angle 1, and explain the reason; (3) If folded into Figure 4, write the relationship between angle A and angle 1, angle 2, and explain the reason; (3) if folded into figure 5, write the relationship between angle A and angle 1, angle 2, and explain the reason

As shown in the picture
①∠1=180°-2x,∠2=180°-2y
So, 1 + 2 = 360 ° - 2 (x + y) = 360 ° - 2 * (180 ° - a) = 2A
②∠2=2∠A
③∠1=2∠A
④∠EDO=∠A+x；∠EOD=∠A+∠2
In △ EOD, x + (﹥ a + x) + (﹥ a + ﹥ 2) = 180 degree
Therefore, 2 ∠ a + 2 + 2x = 180 degree
===> 2∠A+∠2=180°-2x
===> 2∠A+∠2=∠1
⑤ Ditto: 2 ∠ a + 1 = ∠ 2