Step 1. Choose a point on the ball and draw a circle with center on the ball. Choose points , , and on that circle.

Step 2. Draw a triangle congruent to on the paper and construct the center of its circumscribed circle.

Step 3. Draw two mutually perpendicular lines (horizontal and vertical) through . Let be the intersection of the horizontal line with the circle. Find the point on the vertical line such that the segments and are equal. ( is also equal to the segments and .)

Step 4. Find the intersection of the vertical line and the line perpendicular to through .

If the point is opposite on the ball, then triangle is congruent to . So the segment equals the diameter of the ball.

Step 5. To get a segment equal to the ball's radius, construct point , the midpoint of segment .