# Equation of a Circle

• Jan 29th 2008, 03:55 PM
MagicBirdy
Equation of a Circle
Well the knowledge of it I just simply forgot about and don't remember a single thing about how to do it.

Write the equation of a circle with center (4,0) and passing through the point (12,6).

I don't want just an answer, I need the method of how to do it. Also I might also need help understanding this question as well

Write the equation of a circle with center (6,6) and tangent in both axes.

THANKS!!!
• Jan 29th 2008, 03:59 PM
Jhevon
Quote:

Originally Posted by MagicBirdy
Well the knowledge of it I just simply forgot about and don't remember a single thing about how to do it.

Write the equation of a circle with center (4,0) and passing through the point (12,6).

I don't want just an answer, I need the method of how to do it. Also I might also need help understanding this question as well

Write the equation of a circle with center (6,6) and tangent in both axes.

THANKS!!!

the equation of a circle is given by: \$\displaystyle (x - h)^2 + (y - k)^2 = r^2\$

where \$\displaystyle (h,k)\$ is the center and \$\displaystyle r\$ is the radius

so fill in what you know for your circle.

you are also given the additional information that when \$\displaystyle x = 12\$, \$\displaystyle y = 6\$, you can use this to solve for \$\displaystyle r\$

for the second question, you know that the circle passes through (0,6) and (6,0) ........which tells you the radius is 6