To construct a square inscribed in a circle, we need to have two lines that will be used as diagonals of the square we want to draw.
In this case, in the diagram, we already have one line, that is the . The other line we need has to form an angle of 90° with the line BC as shown in the following diagram:
This red line is a perpendicular bisector to diameter BC and is the next step to draw the square. It is called a bisector because it divides BC into two equal angles of 90°.
Answer:
Construct the perpendicular bisector to diameter BC