Find the standard form for the equation of a circle xh2yk2r2
Find the standard form for the equation of a circle (xh)2+(yk)2=r2 with a diameter that has endpoints (10,1) and (1,9).
h=
k=
r=
Solution
endpoints of diameter = (-10,1) and (1,-9)
the centre of the circle would be the midpoint of the diameter
so applying midpoint formula to find the centre
midpoint = ( x1+x2/2) , (y1+y2/2)
plugging the values we get
centre = ( -9/2 , - 4 )
now radius is the diatance from centre to one of the endpoints
applying distance formula
radius = sqrt 221 / 4 = 7.43
therefore, equation of circle is
( x + 9/2)^2 + ( y + 4)^2 = 7.43^2
