Sub coordinates in to get: (1-a)^2 + (3-b)^2 = r^2 , (5-a)^2 + (7-b)^2 = r^2 , (2-a)^2 + (9-b)^2 = r^2

1st and 2nd expanded ; 1-2a+a^2 +9-6b+b^2 = 25-10a+a^2+49-14b+b^2 , 10-2a-6b=74-10a-14b , 8a+8b=64 , a+b=8

1st and 3rd expanded ; 1-2a+a^2+9-6b+b^2=4-4a+a^2+81-18b+b^2 , 10-2a-6b=85-4a-18b , 2a+12b=75

Solve simultaneous equation : a+b=8 // 2a+12b=75 to get a=2.1 and b=5.9 , so (x-2.1)^2+(y-5.9)^2 = r^2

Finally sub in a coordinate to this equation, so for example: (1-2.1)^2+(3-5.9)^2 = r^2, and solve for r^2 which is 9.62

Now we have the equation of the circle, which is (x-2.1)^2+(y-5.9)^2=9.62

	Created by Doc Boff about 8 years ago

Circle questions