Q3 of 63 Page 202

If a circle passes through the point (0, 0) (a, 0), (0, b) then find the coordinates of its centre.

The equation of a circle having centre (h,k), having radius as "r" units, is


(x – h)2 + (y – k)2 = r2



Putting the values of given co-ordinates in the above expression,


(0,0)


(0 – h)2 + (0 – k)2 = r2


h2 + k2 = r2


(a,0)


(a – h)2 + (0 – k)2 = r2


a2 + h2 - 2ah + k2 = r2 ------ (1)


(0,b)


(0 – h)2 + (b – k)2 = r2


h2 + b2 + k2 - 2bk = r2 ------- (2)


On solving equations (1) & (2), respectively,


a (a – 2h) = 0


b (b – 2k) = 0


So,


a = 0 or 2h


b = 0 or 2k respectively.


Since the circle passes through the centre (0,0), so the co – ordinates are


a = 2h,


b = 2k,


Th co – ordinates of the centre are .


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