三角形每條邊的垂直平分線點畫架?20分!

Let AB be one of the sides of the triangle. Use A as the centre, draw an arc with a compasses with radius = length of AB. Similarly, use B as the centre and radius =AB draw an arc. The 2 arcs will intersect at 2 points, join the 2 points which will give the perpendicular bisector of AB. Do the same for the other 2 sides of the triangle.