我们知道:(1)有两边相等的三角形是等腰三角形;(2)线段中垂线上的点到这条线段两端点的距离相等;(3)圆上的点到圆心的距离都等于半径R(定值).如果把这些知识交叉糅合,结合圆规操作,就可以很好地在坐标平面内确定出等腰三角形的顶点位置.下面就此结合两例予以说明. We know that: (1) triangles with equal sides are isosceles triangles; (2) points on vertical lines in the line segment are equal to the points at both ends of the line segment; (3) distances from the point on the circle to the center of the circle are equal to the radius R (fixed value). If you cross-know this knowledge, combined with the compass operation, you can determine the vertex position of the isosceles triangle well in the coordinate plane. Here we combine two examples to illustrate.