Geometry help please

Question

A radio beacon indicates that a certain dolphin is less than 1 miles from boat A and at least 1 1/2 miles from boat B. Boats A and B are 2 miles apart. Draw a simple map showing the locations of the boats and all the places where the dolphin might be located. Be sure to show the scale of your map. Explain how you determined all possible locations for the dolphin. 

Answer 1

1. Draw two points 4 inches apart representing boats A and B. Label them (A and B). Your map scale is 4 inches = 2 miles, or 1 inch = 1/2 mile.
2. Using a circle compass, open it to 2 inches (1 mile). Place the compass point on boat A and draw a circle around boat A. Since the dolphin is less than 1 mile from boat A, it must be somewhere within the 1 mile circle.
3. Now open the compass to 3 inches (1 1/2 miles). Place the point on boat B and draw a circle around boat B. The dolphin is at least 1 1/2 miles fro boat B, so it must be outside of that circle.
4. What part of circle A is outside of circle B? That's where the dolphin is.