## anonymous one year ago How do I find the radius of a circle with a center at (-1, -2), which also passes through point (0,2)?

1. amoodarya

$(x-x_c)^2+(y-y_c)^2=r^2\\center=(-1,-2)\\so\\(x+1)^2+(y+2)^2=r^2\\$ the circle passes through (0,2) |dw:1436385033207:dw| so check the point in equation to find r can you go on ?

2. anonymous

@amoodarya I'm still a little confused. Could you explain further?

3. anonymous

The previous post used the standard form of a circle at center (h ,k) Let h=xc let k= yc then you have a point (0,2) (0,2) (x+1)^2 + (y+2)^2 = r^2 (0+1)^2 + (2+2)^2 = r^2 1+4 = r^2 5= r^2 $r=\sqrt{5}$

4. anonymous

Ok. Thanks