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December 4th, 2006, 03:16 AM  #1 
Newbie Joined: Dec 2006 Posts: 9 Thanks: 0  Need help again
A circle of radius,r with its centre in positive quadrant (x>0,y>0) touches both the x and y axes. This circle also touches the line 3x + 4y = 12 Find A) the two values of r and obtain the equations of the two corresponding circles B) find the forth equation of the fourth tangent to the circle. Have problem with the B) part plz help thz in advance. 
December 8th, 2006, 04:53 AM  #2 
Newbie Joined: Dec 2006 From: Rochester, UK Posts: 17 Thanks: 0 
I think the forth tangent is the tangent to bote circles which is the reflection of 3x+4y=12 with respect to the line joining the centers which is y=x. So the the equation of the new tangent is 3y+4x=12 [just change x to y and y to x.]

December 19th, 2006, 08:54 AM  #3 
Newbie Joined: Dec 2006 Posts: 9 Thanks: 0 
Ya, you're right. But do you have any idea to prove it mathemathically??? THZ FOR HELPING 