# Math Help - i dont get thisss question!!

1. ## i dont get thisss question!!

find the center of the circle that circumscribes triangle ABC.

1. A (0,0),B (6,4),C (6,0)

2. A (-3,11),B (9,11),C (-3,21)

2. Originally Posted by whmandy
find the center of the circle that circumscribes triangle ABC.

1. A (0,0),B (6,4),C (6,0)
just set up and solve the three simultaneous equations.

you know that the equation of a circle is: $(x - a)^2 + (y - b)^2 = r^2$ where $(a,b)$ is the center.

take $(x,y)$ to be $(0,0),~(6,4)$ and $(6,0)$ respectively, you get:

$(0 - a)^2 + (0 - b)^2 = r^2$ .................................(1)
$(6 - a)^2 + (4 - b)^2 = r^2$ .................................(2)
$(6 - a)^2 + (0 - b)^2 = r^2$ .................................(3)

now solve this system for $a$ and $b$ only

the second problem is done similarly