diameter of a circle

Question

the diameter of a circle given the points: (0,11)(-4,7/2) 

and the radius 

Answer 1

the distance formula is D = rad{((X2-X1)^2)+((Y2-Y1)^2)} . Just plugin the values of your x and y. Then the radius is half of the diameter, so divide your distance by 2 and that will be your radius of the circle.