SOLUTION: One of the most famous landmarks in England is the London Bridge that spans the River Thames. Its history can be traced back to the first century and the Roman occupation of Englan

Question 1038640: One of the most famous landmarks in England is the London Bridge that spans the River Thames. Its history can be traced back to the first century and the Roman occupation of England. Since then, multiple structures have spanned the river's banks. The most recent bridge was built in 1960. The previous bridge, built in 1831, was transported, stone by stone, to Lake Havasu, Arizona.
One of the earliest bridges on the site and the first made of stone had twenty arches that were 60 feet high and 30 feet wide.
Write an equation for the ellipse in which the x-axis coincides with the water level and the y-axis passes through the center of the arch. (Assume x and y are measured in feet.)
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Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
The points where the bridge meets the water are
( 15, 0 )
( -15, 0 )
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The form of the equation is:

where is a positive number. This will make it a
parabola with a peak for a vertex, not a minimum.
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The x-value of the vertex is ( given )
is the formula, so , since

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Find the y-value of vertex:

( given )
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So far, I have:

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When , or , so
I can say:
( I could have used )

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So the equation is:

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Here's the plot:

check:
When , does or ?

OK
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