2.6-2: Graphing Circles, Circles around Us

Recall… Standard Form: (x-h) 2 + (y-k) 2 = r 2 – Radius = r – Center (“Centre”) = (h, k)

Graphing Circles Graphing circles requires two pieces of information – 1) Center – 2) Radius Once we know the above information, we can graph using some easy steps

To graph: 1) Locate the center; make this a point 2) Determine the radius 3) Using the radius, proceed that many units to the (from the center): – Right – Up – Left – Down

Example. Graph the circle given by the equation (x+2) 2 + y 2 = 169 – Center? – Radius?

Not the “pretty” form Example. Graph the circle for the equation x 2 + y 2 – 2x + 10y + 1 = 0. Must complete the square for BOTH the variables, x and y Move all constants to the other side

(x 2 – 2x) + (y y) = -1 – Add (b/2) 2 to both sides for both x and y

Circles Around Us

Assignment See “Making Circles” assignment sheet. Due: 10/24

Instead of me telling you the answers, please come to the smart board OR white board and write YOUR answers to the assignment. Pg. 176, 1-21 odd