Answers

2014-06-12T07:12:01+08:00
Let C(h,k)

Given:
 center is on line y = x
and 
tangent to the line y = 5
radius = 2 

from the figure attached

k = 5-2 = 3

center of the line is y=x
or k = h
h  = 3

C(3,3)

therefore, the equation of the line is,
(x-h)²+(y-k)²=r²

(x-3)²+(y-3)²=2²

for the general equation just expand the equation.
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