# Homework Help: Finding equation of a circle

1. Mar 14, 2005

### furtivefelon

hi, this isn't really a physics problem, more of a math problem, however, i can't find a math forum.. so i thought i'd put it here :D

your given that a circle passes through y-axis adn x-axis, also the circle passes through the points (8, -1).. find the equation of the circle, reminded that the equation should be in the following form: (x-h)^2+(y-k)^2=r^2

i have no idea how i should approach this problem, thanks alot for your help :P

2. Mar 14, 2005

### SpaceTiger

Staff Emeritus
What are the other points?

3. Mar 14, 2005

### furtivefelon

that's teh whole question.. that's suppose to be the hardest problem on the sheet, and since there are no any other point, i can't figure it out :|

4. Mar 14, 2005

### dextercioby

What do you mean my passes through "y" & "x" axis...?Shouldn't it be the other way around...? Actually,i think they mean that the circle is tangent to those lines...

I found the radius to be either 8.5,or 0.5.You decide which value is correct...

Daniel.

5. Mar 14, 2005

### furtivefelon

mmm.. yes, it indeed is tangent to the x/y axis.. can you tell me how you got it? i care more about the process than the result :D thank you very much!

6. Mar 14, 2005

### dextercioby

Draw a circle & use geometry in a pythagoreic triangle...

Daniel.