8.2 The hyperbola  (Page 5/13)

The y -coordinates of the vertices and foci are the same, so the transverse axis is parallel to the x -axis. Thus, the equation of the hyperbola will have the form

First, we identify the center, $\left(h,k\right).$ The center is halfway between the vertices $\left(0,\mathrm{-2}\right)$ and $\left(6,\mathrm{-2}\right).$ Applying the midpoint formula, we have

Next, we find $a^2.$ The length of the transverse axis, $2a,$ is bounded by the vertices. So, we can find $a^2$ by finding the distance between the x -coordinates of the vertices.

Now we need to find $c^2.$ The coordinates of the foci are $\left(h\pm c,k\right).$ So $\left(h-c,k\right)=\left(-2,\mathrm{-2}\right)$ and $\left(h+c,k\right)=\left(8,\mathrm{-2}\right).$ We can use the x -coordinate from either of these points to solve for $c.$ Using the point $\left(8,\mathrm{-2}\right),$ and substituting $h=3,$

Next, solve for $b^2$ using the equation $b^2=c^2-a^2:$

Finally, substitute the values found for $h,k,a^2,$ and $b^2$ into the standard form of the equation.

The standard form that applies to the given equation is $\frac{y^2}{a^2}-\frac{x^2}{b^2}=1.$ Thus, the transverse axis is on the y -axis

The coordinates of the vertices are $\left(\mathrm{0,}\pm a\right)=\left(0,\pm \sqrt{64}\right)=\left(\mathrm{0,}\pm 8\right)$

The coordinates of the co-vertices are $\left(\pm b,0\right)=\left(\pm \sqrt{36},0\right)=\left(\pm 6,0\right)$

The coordinates of the foci are $\left(\mathrm{0,}\pm c\right),$ where $c=\pm \sqrt{a^2+b^2}.$ Solving for $c,$ we have

Therefore, the coordinates of the foci are $\left(\mathrm{0,}\pm 10\right)$

The equations of the asymptotes are $y=\pm \frac{a}{b}x=\pm \frac{8}{6}x=\pm \frac{4}{3}x$

Plot and label the vertices and co-vertices, and then sketch the central rectangle. Sides of the rectangle are parallel to the axes and pass through the vertices and co-vertices. Sketch and extend the diagonals of the central rectangle to show the asymptotes. The central rectangle and asymptotes provide the framework needed to sketch an accurate graph of the hyperbola. Label the foci and asymptotes, and draw a smooth curve to form the hyperbola, as shown in [link] .