To find the radius You have to take the circumference of the circle and divide it by 2 times π (pi)
To find the center you draw a chord across the circle (a line across the circle near the edge so it cuts the circumference in two places- if you didn't know) then you find the mid point of the chord, and add a chord or two to determine where they meet in the center
When you have an equation that has variables and you know the value of those variables, just plug it it. So plugging the vaules we get Just evaluating we get 4
