Questions on Geometry: Length, distance, coordinates, metric length answered by real tutors!

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Question 166148: Show that the points (-2,5),(-2,-1) and (4,-1) all lie on a circle whose center is at (1,2). Find the length of the radius.: Show that the points (-2,5),(-2,-1) and (4,-1) all lie on a circle whose center is at (1,2). Find the length of the radius.
Answer by Mathtut(1344) About Me  (Show Source):
You can put this solution on YOUR website!
since C(1,2) is the center if all lie on the circle then the distance between each point and C should be equal and would be the length of the radius.
distance between 2 points is sqrt((change-in-x)^2+(change-in-y)^2)
so distance between the following points and C are:
(-2,5) sqrt((-2-1)^2+(5-2)^2)---->sqrt(-3^2+3^2)=3sqrt(2)
(-2,-1) sqrt((-2-1)^2+(-1-2)^2)--->sqrt(-3^2+-3^2)=3sqrt(2)
(4,-1) sqrt((4-1)^2+(-1-2)^2)---->sqrt(3^2+-3^2)=3sqrt(2)
they all lie on the circle with a radius of 3sqrt(2)