Ellipse Foci Problem.wmv

r1273m

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Published 2009-12-24

Help requested to solve a problem trying to find the foci of an ellipse

All Comments (6)

@videomavric 10 years ago

formula is x^2/a^2 + y^2/b^2 = 1 plug in height: x^2/a^2 + y^2/300^2 = 1 plug in the point (470,240) since we know that is on the ellipse and solve for a to be 783 1/3 next we substitute into the formula c^2 = a^2 - b^2 and find c is 723.6098 mm from the center ergo the foci's coordinates are (0, ±723.6098 mm)
@r1273m 14 years ago

Thanks for the comment though I think as you say it does not give the correct result. It has been suggested that I re-record the video with better labelling of the axes and I will do this next week. Thanks again for trying. Bob
@osmanfb1 13 years ago

same thought process, except the numbers are different: b=300, a= 470/sqrt(1-(270/300)^2) = 1078.25 c=sqrt(a^2-b^2)=1035.68
@DDragontamer 12 years ago

-read comments- BRAIN FART
@kmhsmarinmath 14 years ago

hmm. I tried (x/a)^2 + (y/b)^2 = 1. sub in 470, 240 for x and y. sub in 300 for b. solve for a. I believe a^2 - b^2 = c^2. a and b represent half of each major and minor axes. c represents distance from center to foci. my a = 587.5. then c = 505.13. Still didn't seem correct however.