Question 7: Given the length y of a chord, and the length x of the sagitta, the ________ can be used to calculate the radius of the unique circle which will fit around the two lines:

Question 10: This equation of the circle follows from the ________ applied to any point on the circle: as shown in the diagram to the right, the radius is the hypotenuse of a right-angled triangle whose other sides are of length x − a and y − b.