## anonymous 5 years ago How do you put a half-circle into equation form?

1. anonymous

$x = \sqrt{r^2 - y^2}$ where r is the radius

2. anonymous

thats for the upper half of the circle it's the negative for the bottom half of the circle

3. anonymous

So lets just say that the graph is on (9,0), (0,9), and (-9,0), and those are the dimensions of it. How can I put that into equation form?

4. anonymous

the radius is 9 $x = \sqrt{81 - y^2}$

5. anonymous

Thanks!

6. anonymous

no problem