Activity #6__the Circle with Center through Point tool

The Circle with Center through Point button lets you to draw a circle with a center point and an intersection point. Select your center point first and then select the intersecting point.
DIRECTIONS
1. Adjust the Line Segment AB so that the length is 3.0 (radius is 3.0 as well).[br]2. Click the "Circle with Center Through Point" tool and then click onto point D.[br]3. Move the red curve out until it touches point B.[br][br]4. Now click unto the undo (reverse button) so that you are at the original line.[br]5. Adjust the line Segment AB so that the length is 6.0 (radius is 6). [br]6. Create another circle with the center at point D.
QUESTION
What is the biggest circle you can create so that you can see the entire circle? What is radius of this circle?

Information: Activity #6__the Circle with Center through Point tool