【知识归纳】【例题分析】例1.如图,射线OA与x轴正方向夹角为120°,OA=4,求:(1)点A的坐标;(2)点A关于x轴的对称点B的坐标;(3)以AB为一边的等边△ABC的顶点C的坐标.解:(1)过A作AD⊥x轴于点D,得Rt△AOD,且有∠AOD=60°∵OD=12OA=2,AD=23√,∴点A的坐标为(-2,23√)(2)延长AD到B,使 [Summary of Knowledge] [Example Analysis] Example 1. As shown in the figure, the angle between the positive direction of the ray OA and the x-axis is 120°, OA=4, and the coordinate of the point A is obtained; (2) The point A is related to the x-axis. The coordinates of the symmetry point B; (3) Coordinates of the vertex C of the equilateral △ABC with AB as a side. Solution: (1) Over A for AD ⊥ x axis at point D, Rt ΔAOD, and ∠AOD = 60° ∵ OD=12 OA=2, AD=23 √, coordinate of point A is (-2,23 √) (2) extend AD to B so that