System Of Circles 2

Find the eq. of the circle which cuts orthogonally the circle x2+y2-4x+2y-7=0 having the centre at (2,3)
I tried to use the relation d2=r12+r22 but then i got a quadratic eq. which was really wrong.
Help me.

3 Answers

106
Asish Mahapatra ·

(2,-1) [center of given circle]
d2 = 16
r12 = 12
=> r22 = 4

=> (x-2)2+(y-3)2=4

forgiv calc. errors

1
Sridhar M ·

This is quite simple.

the equation of the circle is

(x-2)2 + (y-2)2 = r2

now expand it and then use the condition for orthogonal circles. You get r=2

3
tormented ·

Oh nice!
Why didn't I think of that :(

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