Question 40114
The midpoint of the diameter is the centre.
Midpoint formula: ({{{(x + x)/2}}},{{{(y + y)/2}}})
({{{(-2 + 6)/2}}},{{{(1 - 5)/2}}})
({{{(4)/2}}},{{{(-4)/2}}})
({{{2}}},{{{-2}}})
The distance from this point to a another point on the circle is the radius.
Distance formula: {{{d = sqrt((x - x)^2 + (y - y)^2)}}}
{{{d = sqrt((2 + 2)^2 + (-2 - 1)^2)}}}
{{{d = sqrt((4)^2 + (-3)^2)}}}
{{{d = sqrt(16 + 9)}}}
{{{d = sqrt(25)}}}
{{{d = 5}}}
Standard form for circle: {{{(x - h)^2 + (y - k)^2 = r^2}}}
{{{(x - 2)^2 + (y + 2)^2 = 25}}}