Section 9-2 Graphing Circles 1 General form for a circle Represents the center of the circle Represents a point on the circle Represents the radius of the circle General form for a circle centered at the origin

Example: Graph the following equation 2

3 We need to complete the square, collect terms, get constant by itself Now to complete the square divided 6 by 2 and square, divide -4 by 2 and square Add the same to the other side of the = sign Write as quantity’s squared

Example: Graph the following equation 4 We need to complete the square, collect terms, get constant by itself Now to complete the square divided -10 by 2 and square, divide 8 by 2 and square Add the same to the other side of the = sign Write as quantity’s squared

Example: Graph the following equation 5 We need to complete the square, collect terms, get constant by itself Now to complete the square divided 4 by 2 and square Add the same to the other side of the = sign Write as quantity’s squared

We can also write the equation for a circle if we know a point and the center all we need is the general form. Example: write the equation of the circle with the following information: Center Point 6 Plugging in the values we can solve for r 2 and plug the center and r 2 into the general form again Using this value we can write our equation

We can also write the equation for a circle if we know a point and the center all we need is the general form. Example: write the equation of the circle with the following information: Center Point 7 Plugging in the values we can solve for r 2 and plug the center and r 2 into the general form again Using this value we can write our equation

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