Graphing Circles

http://www.gdawgenterprises.com

This video shows how to graph circles starting with the standard form for the equation of a circle. From the standard form, algebra is used to isolate the y variable, then graphed. Special emphasis is placed on the h and k constants. The x minus a number moves the circle to the right and x plus a number moves the circle to the left. The y minus a number moves a circle up and the y plus a number moves a circle downward. The conics application in the TI 84 series calculators is used to check answers. Example problems are given as well.

Background music: Drifting by Andy McKee

Category:

Education

Tags:

• gdawg
• gdawgrapper
• graphing
• circles
• conics
• algebra
• two
• standard
• form
• of
• circle
• TI83+
• ti83plus
• TI84+
• TI84Plus

[JosephJonLombardi]

Dude, you did the first circle wrong when calculating on your calculator under conics after you hit trace key. you said x=-2, y=6. wrong

[gdawgrapper]

@JosephJonLombardi At first I saw your comment and looked at the video and wondered how it was wrong, but then I put those values in my calculator again. Somehow in making the video, I drew a circle with an h = -2 instead of +2 so that circle shown is the wrong one as you said. It should be 4 units to the right and the top of it should be x=2 and y=6. Good call and sorry for the mistake. I hope it didn't cause you too much trouble. Thanks for viewing and commenting.

[gdawgrapper]

@XxFightinDirtyxX Do you see that (x-2)^2 on the left of the equation? That lets us know that the centerof the circle will be found where x = 2 (positive 2). And from that value, +2, I know that going to the right 9 units and to the left 9 units will the left and right edges. Why is that? Because of the # at the right of the equation, 81. I know that 81 is the radius^2, so the radius is the square root of that number, telling me to choose inputs of -7 and 11 to get edges. Let me know.

[gdawgrapper]

@XxFightinDirtyxX Negative 7 and 11 were two of the other numbers and I picked them because they give us the left and right edges of the circle. The remaining input value I used, 5, I just made up. I could have chosen a lot of different input values and still have had a good outline of a circle. Even though your comment was addressed to JosephJonLombardi, it seemed to be asked in my direction as the video author. Thanks for viewing and commenting.

[JosephJonLombardi]

@gdawgrapper No problem. I am reviewing Algebra for the compass test to get into Calculus. I couldn't do the circle problems on the sample test. Your video reminded me how to do it, it was very helpful. Thank you!

[blupi151]

Thank for this insightful video, it was very much appreciated sir.

[Creamfan121]

Parabolas must be the simplest conic to graph... -_-'

[NateHail]

does andy mckee know you are using his music?!?!?!? lol

[brooksjbennett]

thank you soooo much for the video! It really cleared some things up for me!

[robo2000nitro]

thanks for the video