SOLUTION: Find the equation of the ellipse with x intercepts at (±6, 0) and y intercepts at (0,±4) and find the foci.

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Question 334889: Find the equation of the ellipse with x intercepts at (±6, 0) and y intercepts at (0,±4) and find the foci.
Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
Find the equation of the ellipse with x intercepts at (±6, 0) and y intercepts at (0,±4) and find the foci.




The vertices are marked with V's, the foci with F's

Ellipses which have this shape (like an egg sitting on a table,
not like the number "0") have this equation (learn it):

x%5E2%2Fa%5E2%22%22%2B%22%22y%5E2%2Fb%5E2%22%22=%22%221


The green line is a, which is 6 units long, called the semi-major axis
The purple line is b, which is 4 units long, called the semi-minor axis,
so the equation of the ellipse is

x%5E2%2F6%5E2%22%22%2B%22%22y%5E2%2F4%5E2%22%22=%22%221

or

x%5E2%2F36%22%22%2B%22%22y%5E2%2F16%22%22=%22%221

The foci (±c,0) are found by this Pythagorean equation for all ellipses:

c%5E2=a%5E2-b%5E2
c%5E2=6%5E2-4%5E2
c%5E2=36-15
c%5E2=20
c=sqrt%2820%29
c=sqrt%284%2A5%29
c=2sqrt%285%29

The foci are F1%282sqrt%285%29%2C0%29 and F2%28-2sqrt%285%29%2C0%29

Edwin