Eccentricity
I forgot how to find the eccentricities of narrow vs. wide ellipses vs. circles. I know wide ellipses have an eccentricity close to 1, circles have an eccentricity of 0 (since focal length is 0), but then what are narrow ellipses? I seem to remember eccentricity must be greater than 0, so is it also between 0 and 1 for narrow ellipses?
Also, for number 8 on the pretest, I'm coming up with y=-15/2, since x^2+16=32 is the same as x^2=32(y-1/2), so 4p=32, and p=8, so the directrix of the parabola would be y=1/2-8=-15/2, which isn't an option. Where did I go wrong, or is the 16 a mistake on the test?
Also, for number 8 on the pretest, I'm coming up with y=-15/2, since x^2+16=32 is the same as x^2=32(y-1/2), so 4p=32, and p=8, so the directrix of the parabola would be y=1/2-8=-15/2, which isn't an option. Where did I go wrong, or is the 16 a mistake on the test?
posted by Kevin S. at 11:27 PM
1 Comments:
When the eccentricity is greater than zero the graph is a hyperbola. I don't think that the eccentricity is related to which is the major axis.
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