Chapter 7: Problem 8
Graph the hyperbola. Find the center, the lines which contain the transverse and conjugate axes, the vertices, the foci and the equations of the asymptotes. $$ \frac{(x-4)^{2}}{8}-\frac{(y-2)^{2}}{18}=1 $$
Short Answer
Expert verified
Center: (4, 2); Vertices: (4±2√2, 2); Foci: (4±√26, 2); Asymptotes: y = 2 ± 3/2(x-4); Transverse axis: along x.
Step by step solution
01
Identify the Standard Form
The given equation of the hyperbola is \( \frac{(x-4)^{2}}{8}-\frac{(y-2)^{2}}{18}=1 \). This is in the standard form for a hyperbola: \( \frac{(x-h)^{2}}{a^{2}} - \frac{(y-k)^{2}}{b^{2}} = 1 \), where \((h, k)\) is the center, \(a^{2} = 8\), and \(b^{2} = 18\).
02
Determine the Center
From the standard form \((x-h)^{2}\) and \((y-k)^{2}\), the center \((h, k)\) is \((4, 2)\).
03
Calculate the Vertices
The vertices are located \(a\) units from the center along the transverse axis. Here, \(a^2 = 8\) so \(a = \sqrt{8} = 2\sqrt{2}\). Since the hyperbola is horizontal (as it subtracts the \(y\) term), the vertices are at \((4 \pm 2\sqrt{2}, 2)\).
04
Find the Foci
Calculate \(c\) using \(c^{2} = a^{2} + b^{2}\). So, \(c^{2} = 8 + 18 = 26\) and \(c = \sqrt{26}\). The foci are at \((4 \pm \sqrt{26}, 2)\).
05
Determine Asymptotes
The asymptotes for a horizontal hyperbola are given by \(y = k \pm \frac{b}{a}(x-h)\). Here, \(k = 2\), \(h = 4\), \(a = 2\sqrt{2}\), and \(b = 3\sqrt{2}\). Thus, the asymptotes are \(y = 2 \pm \frac{3\sqrt{2}}{2\sqrt{2}}(x-4)\), simplifying to \(y = 2 \pm \frac{3}{2}(x-4)\).
06
Transverse and Conjugate Axes
The transverse axis is parallel to the \(x\)-axis and includes the points \((4 \pm 2\sqrt{2}, 2)\). The conjugate axis is parallel to the \(y\)-axis and is not directly visible from the equation; it includes points vertically centered at \((4, 2 \pm 3\sqrt{2})\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Center of a Hyperbola
The center of a hyperbola is the midpoint around which the hyperbola opens. This point functions similarly to the center of a circle or an ellipse, but in the case of the hyperbola, it signifies where the branches start to diverge in the opposite directions. The general equation of a hyperbola in standard form is \( \frac{(x-h)^{2}}{a^{2}} - \frac{(y-k)^{2}}{b^{2}} = 1 \). In this equation, \((h, k)\) represents the center. Let’s look at the exercise example:
- The given equation is \( \frac{(x-4)^{2}}{8} - \frac{(y-2)^{2}}{18} = 1 \). This indicates that the center of the hyperbola is at \((4, 2)\).
- The center is determined by the values inside the parentheses: \((x-h)\) and \((y-k)\).
Defining the Vertices of a Hyperbola
Vertices are the points on the hyperbola that lie closest to the center on its branches. They help in understanding how the hyperbola is oriented. For a horizontal hyperbola, vertices extend along the x-axis from the center. Here's how we find them:
- Vertices are located \(a\) units away from the center along the transverse axis. In our example, \(a^2 = 8\), which gives \(a = \sqrt{8} = 2\sqrt{2}\).
- Since the hyperbola is horizontal, the calculation leads to vertices at \((4 \pm 2\sqrt{2}, 2)\).
Finding the Foci of a Hyperbola
The foci (singular: focus) are key points that further define the hyperbola's shape. They represent the points from which the distances to any point on the hyperbola differ by a constant amount. To find the foci:
- We calculate \(c\) using the relationship \(c^{2} = a^{2} + b^{2}\). For our equation, \(c^{2} = 8 + 18 = 26\), so \(c = \sqrt{26}\).
- In this horizontal hyperbola, the foci are positioned at \((4 \pm \sqrt{26}, 2)\).
Understanding the Asymptotes of a Hyperbola
Asymptotes are lines that the hyperbola approaches but never actually touches. They give the hyperbola its unique open-ended shape. For hyperbolas, these lines are a crucial guide for sketching their branches.To find the asymptotes, we use the following formula for a horizontal hyperbola:
- The equation: \(y = k \pm \frac{b}{a}(x-h)\).
- From the given example, substituting the values: \(k = 2\), \(h = 4\), \(a = 2\sqrt{2}\), \(b = 3\sqrt{2}\).
- This results in the asymptotes being \(y = 2 \pm \frac{3}{2}(x-4)\).