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用一张白纸,可以折出各种大小不同的角。折出的有些角不需要用量角器量就能知道它的大小,比如:将直角对折后的角是45°;有些角只要量出或已知一个角的度数,就能算出另外一个角的度数。不过,在计算折出来的角的度数时,通常先要根据纸张和折角的特点找出隐蔽条件,再利用隐蔽条件进行计算。例1.如图1,将一张长方形白纸的一个直角翻起折叠(折痕的一端在长方形的一个顶点上),如果∠1=55°,你能说出∠2有多少度吗?
With a piece of white paper, you can roll out a variety of different sizes of angles. Some of the folded corner do not need to use the amount of angular measure to know its size, such as: the right angle after folding the angle is 45 °; some angle as long as the amount of known or known angle, can calculate the angle of the other angle . However, when calculating the degree of the folded corner, it is usually necessary to find the hidden condition according to the characteristics of the paper and the folded corner, and then use the hidden condition to calculate. Example 1. As shown in Figure 1, fold a rectangular sheet of rectangular paper up and down with one end of the crease on the apex of the rectangle. If ∠1 = 55 °, how many degrees can you say ∠2?