What don't you understand? On the xy coordinate system, plot the points to get a general idea of what the triangle looks like. Then find the lengths of DE, EF, and DF using the distance formula as posted earlier. For example, the distance from D(1, 3) to E(-2, -2) is found by:

Similarly, find the other lengths of the triangle and compare them. You know that equilateral triangles have equal sides, isoceles triangles have 2 equal sides, and scalene triangles have no equal sides.

For the questions involving the circle, you did it for r = 3. It's not any different using r = 10 and r =

.