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 March 15th, 2014, 03:53 AM #1 Newbie   Joined: Jun 2013 Posts: 10 Thanks: 0 Analytic Geometry how to sketch a ellipse(x^2/25+y^2/9=1) according to scale using computer? Pls help me. Thx
 March 15th, 2014, 06:46 AM #2 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,344 Thanks: 2466 Math Focus: Mainly analysis and algebra Re: Analytic Geometry Why do you specify the use of a computer? Is it not easy to sketch that equation by hand? You know roughly what an ellipse looks like. By setting $x=0$ and solving for y you will find the intercepts with the y-axis. Setting $y= 0$ and solving for x will give you the intercepts with the x-axis. If you need further information, you can differentiate with respect to x, which will allow you, for any point on the x,y-plane, to determine the gradient of the solution at that point (assuming that a solution exists there). Marking a few of these gradients will allow you to draw a pretty accurate solution. This is plotting the gradient field of the function and an example can be seen here http://upload.wikimedia.org/wikipedi...lfield.svg.png. If you definitely need to use a computer, you should perhaps work at finding a parametric expression of the equation so that $x = f(\theta) y = g(\theta)$ A computer can then plot lots of points and join them up. All you have to do is decided what interval of $\theta$ is appropriate, and how many points to plot in that interval. When you have that much, you'll be able to find lots of websites that will do the plotting for you.
March 15th, 2014, 10:19 AM   #3
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Re: Analytic Geometry

Quote:
 Originally Posted by tkttan how to sketch a ellipse(x^2/25+y^2/9=1) according to scale using computer?
Same as: 9x^2 + 25y^2 = 225

March 15th, 2014, 10:51 AM   #4
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Re: Analytic Geometry

Quote:
 Originally Posted by tkttan how to sketch a ellipse(x^2/25+y^2/9=1) according to scale using computer? Pls help me. Thx
We know the vertical semi-axis is 3 units and the horizontal semi-axis is 5 units, so using W|A and the command:

x^2/25+y^2/9=1 where x=-5 to 5, y=-3 to 3

produces:

http://www.wolframalpha.com/input/?i...2C+y%3D-3+to+3

edit: for some reason URLs are no longer parsing as such. Copy and paste the link between the tags into your browser.

 March 15th, 2014, 06:26 PM #5 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,344 Thanks: 2466 Math Focus: Mainly analysis and algebra Re: Analytic Geometry While your post is completely accurate, I have my doubts as to the amount of mathematics the OP will learn from it.
 March 17th, 2014, 05:39 AM #6 Global Moderator   Joined: Dec 2006 Posts: 19,294 Thanks: 1686 When posting a link containing the "^" symbol, replace each occurrence of that symbol with "%5E". Thanks from Evgeny.Makarov
 June 14th, 2014, 07:03 AM #7 Banned Camp   Joined: Feb 2013 Posts: 224 Thanks: 6 Hard or Easy? I can give you an easy answer and a hard answer. Easy: Pop it in GeoGebra. Hard: Understand what an ellipse is. https://www.flickr.com/photos/859374...57638166084655 Reward for doing it the hard way. https://www.flickr.com/photos/859374...57638166084655 https://www.flickr.com/photos/859374...57638166084655

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