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Mathematics 22 Online
OpenStudy (dannyrod2000):

Conic sections help!

OpenStudy (dannyrod2000):

(x-5)^2/4+(y+3)^2/16=1

OpenStudy (dannyrod2000):

need to find vertices, foci, eccentricity, length of major and minor axis

OpenStudy (misty1212):

HI you know what shape this is?

OpenStudy (dannyrod2000):

yes a circle and its center is (5,-3)

OpenStudy (misty1212):

if you know the shape, and the center , the rest its easy no, it is not a circle

OpenStudy (misty1212):

although you did get the center right

OpenStudy (dannyrod2000):

an oval?

OpenStudy (misty1212):

yeah which math teacher call "ellipse"

OpenStudy (dannyrod2000):

ok yeah i know what that is

OpenStudy (misty1212):

so you got the center, next question|dw:1462916268657:dw| is this

OpenStudy (dannyrod2000):

yes

OpenStudy (misty1212):

which one ?

OpenStudy (dannyrod2000):

the vertical one

OpenStudy (misty1212):

yes

OpenStudy (misty1212):

so almost done

OpenStudy (dannyrod2000):

ok what next?

OpenStudy (misty1212):

you got \[\frac{(x-h)^2}{a^2}+\frac{(y-k)^2}{b^2}=1\]

OpenStudy (misty1212):

you got the center and you know it is vertical because the bigger number is under the y term so if \(b^2=16\) that makes \(b=4\) vertices are 4 units above and below the center \((5,-3)\)

OpenStudy (misty1212):

you got that ?

OpenStudy (dannyrod2000):

yes that help me a lot

OpenStudy (misty1212):

also \(a^2=4\) so \(a=2\) minor axis is 2 units left and right of the center \((5,-3)\) that also tells you the length of the minor axis 4 and the length of the major axis, from \((5,-7)\) to \((5,1)\) is 8

OpenStudy (misty1212):

all that is left is the focus

OpenStudy (misty1212):

you know how to find that one?

OpenStudy (dannyrod2000):

all the explanation is understandable so far thanks

OpenStudy (dannyrod2000):

um no i dont sorry

OpenStudy (misty1212):

to find the focus, you need \(c\) which is \(c^2=b^2-a^2\)

OpenStudy (misty1212):

in your case you have \[c^2=16-4=12\] so \[c=\sqrt{12}=2\sqrt3\]

OpenStudy (misty1212):

starting at the center, \((5,-3)\) go up \(2\sqrt3\) and down \(2\sqrt3\)

OpenStudy (misty1212):

which looks silly when you write it for example one of them is \[(5,-3-2\sqrt3)\]

OpenStudy (misty1212):

the other with a plus

OpenStudy (misty1212):

oh one more you need eccentricity that is just \(\frac{c}{a}\) you have both those numbers

OpenStudy (dannyrod2000):

thanks so much for all ur help :)

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