How do you find the equation of the circle, center C(4,-8), tangent to the y-axis?
1 Answer
Jan 29, 2016
# (x - 4 )^2 + (y + 8 )^2 = 16 #
Explanation:
The equation of a circle is :
# (x-a)^2 + (y - b )^2 = r^2# (a , b ) are the coordinates of the centre and r , the radius.
The centre is given ( 4 , -8 ) . Require the radius r .
Since the y-axis is a tangent then the distance from centre
to the y-axis is 4 units. Hence r = 4 .
equation is :
# (x - 4 )^2 + (y + 8 )^2 =4^2#
#(x - 4 )^2 + (y + 8 )^2 = 16#
