Equations and Graphs of Circles: looking for lessons, links  TOPIC_SOLVED

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Equations and Graphs of Circles: looking for lessons, links  TOPIC_SOLVED

Postby 4mase on Mon Apr 06, 2009 10:05 pm

I just need some links and information regarding this. For some reason I just haven't been able to grasp the concept of math lately and I am on my last lesson to. :(

Anyway

Help me please!
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Postby stapel_eliz on Mon Apr 06, 2009 10:39 pm

Try here. :wink:
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Re: Equations and Graphs of Circles: looking for lessons, links

Postby Amuselvrx3 on Sun Apr 12, 2009 9:04 pm

An easy basic start to recognizing equations of circles is that they have both an X squared and a Y squared. However, when you start comparing this equation to other types of graphs ie parabolas,hyperbolas, etc. it can get tricky so thats just a basic start!

Heres an example of how to find points to graph on a circle:
x^2+2X+Y^2+14Y-31=0

first, subtract the 31 from both sides,
X^2+2X+Y^2+14Y=-31

then complete the squares for X and Y

X^2+2X+1+Y^2+14Y+49

add the 1 and 49 you calculated from completing the square to the -31

X^2+2X+1+Y^2+14Y+49=81

Then factor the squares of x and y into an equation

(X+1)2+(Y+7)2=81

you can now decipher the radius and the center point of your cirle. since r^2=81 r=9, and your center is (-1,-7) just the opposite values of your X and Y equations. once you plot your center point, you move up,down, left, and right the number of spaces the radius is. so in this case you would go up, down, left, and right nine spaces.

Hope i helped! =]
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Re: Equations and Graphs of Circles: looking for lessons, links

Postby garner10 on Mon Apr 13, 2009 2:12 am

I found this site to be helpful:
http://www.analyzemath.com/CircleEq/CircleEq.html
good luck!!!
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