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Key concepts
Any conic may be determined by a single focus, the corresponding eccentricity, and the directrix. We can also define a conic in terms of a fixed point, the focus
at the pole, and a line, the directrix, which is perpendicular to the polar axis.
A conic is the set of all points
where eccentricity
is a positive real number. Each conic may be written in terms of its polar equation. See
[link] .
The polar equations of conics can be graphed. See
[link] ,
[link] , and
[link] .
Conics can be defined in terms of a focus, a directrix, and eccentricity. See
[link] and
[link] .
We can use the identities
and
to convert the equation for a conic from polar to rectangular form. See
[link] .
Section exercises
Verbal
Explain how eccentricity determines which conic section is given.
If eccentricity is less than 1, it is an ellipse. If eccentricity is equal to 1, it is a parabola. If eccentricity is greater than 1, it is a hyperbola.
t he silly nut company makes two mixtures of nuts: mixture a and mixture b. a pound of mixture a contains 12 oz of peanuts, 3 oz of almonds and 1 oz of cashews and sells for $4. a pound of mixture b contains 12 oz of peanuts, 2 oz of almonds and 2 oz of cashews and sells for $5. the company has 1080
Lairene and Mae are joking that their combined ages equal Sam’s age. If Lairene is twice Mae’s age and Sam is 69 yrs old, what are Lairene’s and Mae’s ages?