SOLUTION: Find the equation of the hyperbola with vertices at (-4,2) and (0,2) and foci at (-5,2) and (1,2).

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Question 1206860: Find the equation of the hyperbola with vertices at (-4,2)
and (0,2) and foci at (-5,2) and (1,2).

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
The vertices and foci lie on the horizontal line y=2, since all their y-coordinates have y-coordinate 2.

It looks like this:


Therefore the hyperbola has the equation

%28x-h%29%5E2%2Fa%5E2-%28y-k%29%5E2%2Fb%5E2%22%22=%22%221

where the vertex is the midpoint between vertices, and also the midpoint
between foci. That is, the vertex is (-2,2).

a = semi-transverse axis = distance from center to vertex = 2 units
c = semi-conjugate axis = half the height of defining rectangle = sqrt%285%29

Find the equation of the hyperbola with vertices at (-4,2) 
and (0,2) and foci at (-5,2) and (1,2).

So we have the center, so we can determine everything about the equation
except b.

(h,k) the center = (-2,2), a=2

%28x%2B2%29%5E2%2F2%5E2-%28y-2%29%5E2%2Fb%5E2%22%22=%22%221

We use the Pythagorean relation for hyperbolas to find b:

c%5E2=a%5E2%2Bb%5E2
3%5E2=2%5E2%2Bb%5E2
9=4%2Bb%5E2
5=b%5E2  <-- what we need for the denominator:
sqrt%285%29=b

%28x%2B2%29%5E2%2F2%5E2-%28y-2%29%5E2%2F5%5E%22%22%22%22=%22%221
%28x%2B2%29%5E2%2F4-%28y-2%29%5E2%2F5%5E%22%22%22%22=%22%221  <--answer



The defining rectangle is in green.
The blue line is the transverse axis, 2a or 4 in length
The red line is the conjugate axis 2b or 2sqrt%285%29 in length.
The gold lines are the asymptotes of the hyperbola, the extended diagonals
of the defining rectangle.

Edwin