1.两条直线相交得到四个角这里是指两直线相交所成角中小于平角的四个角.如图1中的∠1、∠2、∠3、∠4.这四个角的共同点是:有公共顶点O.不同点是∠1、∠3(∠2、∠4)没有公共边,而∠1、∠2(∠2、∠3等)只有一条公共边(位置关系).前 1. Two lines intersect to get the four corners. Here we mean the four angles that are intersected by the two lines are less than the flat corners. As shown in Figure 1, ∠1, ∠2, ∠3, ∠4. These four corners are common to each other. The point is: There is a common vertex O. The difference is that ∠ 1, ∠ 3 (∠ 2, ∠ 4) have no common edges, while ∠ 1, ∠ 2 (∠ 2, ∠ 3, etc.) have only one common edge (positional relationship). before