Posted by Amanda on Tuesday, April 21, 2009 at 4:30pm.
I have no idea how to do these problems:
Find an equation of each circle.
1. Center (3,5); tangent to the x axis
2. Center (5,3); tangent to the y axis
3. Tangent to the x axis, y axis, and the line y=5 (two answers)
I just really need help understanding how to do this.

Circles (Conic Sections)  Reiny, Tuesday, April 21, 2009 at 4:35pm
1. Did you sketch or just visualize the circle?
Isn't the radius 5 ?
so (x3)^2 + (y5)^2 = 25
2. Do it the same way.
3. y = 5 is a horizontal line 5 units above the xaxis.
I can visualize a circle in the first quadrant, and another in the second quadrant.
isn't the diameter 5 ?
so isn't the centre 2.5 up from the xaxis and 2.5 to the right of the yaxis?
mmmh?