1, ① indicates the point set on the perpendicular of line segment AB; ② represents the point set on a circle with O as the center and 3 as the radius;

2. This set represents the outer center of the triangle;

3. Set A represents a point on a straight line 2x-y=0, and set B represents a point on a straight line 3x+y=0. Then A∩B represents the intersection of two straight lines, and it is enough to solve the equations, so that: x=0, y = 0, then A ∩ b = {(0,0)}. .

A∩C=φ

(A∩B)∩( B∩C)= {(0，0)，(3/5，-9/5)}