聪明的同学,你认识下面的这些图形吗?它们有什么共同的特点呢?飞机、蜻蜓、蝴蝶、京剧脸谱的用处、材料完全不同,但是它们的形状却有一个共同特点——对称。那就是沿着一条直线对折后,这些图形的左边和右边是一样的,就是能够完全重合。因此我们说它们都是对称的,像这样的图形就叫作轴对称图形,这条线叫作对称轴。 Clever classmates, do you know these figures below? What are their common characteristics? The use of planes, dragonflies, butterflies and Beijing Opera masks is completely different, but their shapes have one thing in common: symmetry. That is, after folding along a straight line, the left and right sides of these figures are the same, that is, they can completely coincide. So we say that they are all symmetrical, and a figure like this is called an axisymmetric figure, which is called the axis of symmetry.