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Weird Parabola Problem

  • Thread starter pythagman
  • Start date
  • #1
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Homework Statement


A parabolic communications antenna has a focus 6 feet above its vertex. Write an equation for the parabola and find the width of the antenna 9 feet from the vertex. Locate the origin strategically.


Homework Equations



y= x^2 (parent equation for parabola)

The Attempt at a Solution


focus = 4p.
standard form of parabola , (x-h)^2 = 4p(y-k)^2
4 * 6 = 24 so (x-h)^2 = 24(y-k)^2.
It doesn't give you the origin how are you supposed to write the formula?
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
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(h,k) is the vertex. You can put the origin anywhere you like. Why not put it at the vertex? So (h,k)=(0,0). Now what's the y coordinate 9 feet from the vertex? BTW, check your standard form for a parabola. You've got an extra square in there.
 
  • #3
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Hello...

You've got an extra square in there.
I believe you're right. The equation is (x-h) = 4p(y-k)^2

or (y-k) = 4p(x-h)^2

So, just try x = 24y^2 and work from there ^^
 

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