Finding a Circle Equation

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I'm having trouble trying to figure out how to come to an equation of a circle with this information.

Directions: Find the equation of the Circle described.

Center (0,5); passes through (0,0).

Can anyone help??
Thanks so much!!
 
Equation of a circle having center (a,b) and radius r is
(x-a)^2 + (y-b)^2 = r^2

Now the circle has center (0,5) and passes through (0,0) which means the radius r = 5

So equation of circle becomes
(X-0)^2 + (Y-5)^2 = 5^2

X^2 + (Y-5)^2 = 5^2

Can you simplify from here?
 
babycakes0509 said:
I'm having trouble trying to figure out how to come to an equation of a circle with this information.

Directions: Find the equation of the Circle described.

Center (0,5); passes through (0,0).

Can anyone help??
Thanks so much!!
Click to expand...

The equation of a circle with center (h, k) and radius r is
(x - h)<SUP>2</SUP> + (y - k)<SUP>2</SUP> = r<SUP>2</SUP>

Your circle has its center at (0, 5), so h = 0 and k = 5.
r is the distance from the center to any point on the circle. How far is it from (0, 5) to (0, 0)? (Draw a sketch....it may help you).

Once you know the value of r, simply substitute the values of h, k, and r into the equation.

I hope this helps you.
 
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