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Mathematics 15 Online
OpenStudy (anonymous):

Find the standard form of the equation of the ellipse and give the location of its foci.

OpenStudy (anonymous):

OpenStudy (anonymous):

please explain

OpenStudy (fanduekisses):

Do you know how to find major axis and minor axis?

OpenStudy (anonymous):

no ma'am

OpenStudy (fanduekisses):

major axis= 2a, minor axis=2b

OpenStudy (fanduekisses):

look at the graph

OpenStudy (anonymous):

looking o.o

OpenStudy (fanduekisses):

do you know where the major axis is?

OpenStudy (fanduekisses):

half of the value of the major axis is a (we need a and b for the equation)

OpenStudy (aum):

semi-major axis is 7 and the semi-minor is 6.

OpenStudy (fanduekisses):

yes :)

OpenStudy (fanduekisses):

7 is a and 6 is b

OpenStudy (fanduekisses):

the standard equation for an ellipse ( in this case it is vertical ellipse because the major axis is in the y axis) \[\frac{ x^{2} }{ b^{2} } + \frac{ y^{2} }{ a^2 }=1\]

OpenStudy (anonymous):

So I'm supposed to plug in the major axis and the minor axis into a and b? and if the major axis is in the x-axis it's a horizontal ellipse?

OpenStudy (aum):

\(\Large \frac{ x^{2} }{ a^{2} } + \frac{ y^{2} }{ b^2 }=1 \) You can quickly verify where 'a' and 'b' should be by setting y = 0 and finding the x-intercepts or setting x = 0 and finding the y-intercepts.

OpenStudy (fanduekisses):

yes

OpenStudy (anonymous):

I see... do the x and y need numbers plugged into them too?

OpenStudy (fanduekisses):

no

OpenStudy (aum):

Plug in values for 'a' and 'b'.

OpenStudy (fanduekisses):

can you tell us what you get for the equation?

OpenStudy (fanduekisses):

when you plug in

OpenStudy (aum):

The major axis is along x-axis so 'a^2' should go under the x-term.

OpenStudy (anonymous):

\[\frac{ x^2 }{ 49 } + \frac{ y^2 }{ 36 } = 1\]

OpenStudy (fanduekisses):

oops sorry about that

OpenStudy (anonymous):

o.o dang it

OpenStudy (fanduekisses):

yes that is correct

OpenStudy (anonymous):

Ooooh lol sorry

OpenStudy (fanduekisses):

but your equation is correct ^_^

OpenStudy (anonymous):

thank you guys...what do I do next? o.o

OpenStudy (fanduekisses):

ok now let's find the Foci

OpenStudy (fanduekisses):

Foci of a Horizontal ellipse: (h+-c,k)

OpenStudy (fanduekisses):

The vertex is (h,k), for this ellipse, its vertex is at the origin (0,0)

OpenStudy (anonymous):

Woah there...sorry I just got confused e.e

OpenStudy (anonymous):

oh wait nvm I see it

OpenStudy (fanduekisses):

the foci of a horizontal ellipse: (h+-c,k) the +- means plus or minus)

OpenStudy (fanduekisses):

to find c you use: \[ c^{2}=a^{2}-b^{2}\]

OpenStudy (anonymous):

\[c^2 = 7^2 - 6^2\] then shouldn't c^2 be 1^2 ? but in my calc I did 49 - 36 and got 13... would I make that \[\sqrt{13}\]

OpenStudy (fanduekisses):

yes

OpenStudy (aum):

Yes. One focus at \(\large (+\sqrt{13}, 0) \) and another at \(\large (-\sqrt{13}, 0) \)

OpenStudy (fanduekisses):

I agree with aum

OpenStudy (aum):

FYI: In a parabola (h,k) is the vertex. In ellipse and hyperbola, (h,k) is the center.

OpenStudy (fanduekisses):

correct,lol sorry, I am in pre-calculus hehe I'm learning as well,but thank you aum :)

OpenStudy (anonymous):

Thank you both ^-^ I wish I could give you both medals /.\ I appreciate your help <3

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