(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