Chapter 10: Problem 8
Find the vertices, foci, and asymptotes of the hyperbola, and sketch its graph. $$x^{2}-y^{2}+4=0$$
Short Answer
Expert verified
Vertices: (2,0), (-2,0); Foci: (2√2,0), (-2√2,0); Asymptotes: y = ±x.
Step by step solution
01
Simplify the Equation
We begin with the equation of the hyperbola: \[ x^2 - y^2 + 4 = 0 \]Add 4 to both sides to simplify it:\[ x^2 - y^2 = -4 \] Divide every term by -4 to match the standard form:\[ \frac{x^2}{4} - \frac{y^2}{4} = 1 \] This represents a hyperbola centered at (0,0) with its transverse axis along the x-axis.
02
Identify the Vertices
From the standard form, \( \frac{x^2}{4} - \frac{y^2}{4} = 1 \), the hyperbola has the form \( \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1 \), where \( a^2 = 4 \) and \( b^2 = 4 \). So, \( a = 2 \) and the vertices are located at (+/-a, 0). Thus, the vertices are at (2, 0) and (-2, 0).
03
Determine the Foci
The foci of the hyperbola can be found using the formula \( c^2 = a^2 + b^2 \). Substitute the values \( a^2 = 4 \) and \( b^2 = 4 \):\[ c^2 = 4 + 4 = 8 \] \( c = \sqrt{8} = 2\sqrt{2} \).Thus, the foci are at \( (2\sqrt{2}, 0) \) and \( (-2\sqrt{2}, 0) \).
04
Find the Asymptotes
The asymptotes of the hyperbola are given by the equations\[ y = \pm \frac{b}{a}x \]. Substitute the values \( a = 2 \) and \( b = 2 \): \[ y = \pm \frac{2}{2}x \] \[ y = \pm x \] These are the equations of the asymptotes.
05
Sketch the Hyperbola
To sketch the hyperbola, plot the center at (0,0), the vertices at (2,0) and (-2,0), and the asymptotes as the lines \( y = x \) and \( y = -x \). Draw the hyperbola opening left and right along the x-axis and approaching the asymptotes as it extends.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertices of a Hyperbola
The vertices of a hyperbola are like anchor points that tell us where the hyperbola begins to curve away. In the equation \( \frac{x^2}{4} - \frac{y^2}{4} = 1 \), we can determine the vertices using the variable \(a\), which represents half the distance between the vertices along the transverse axis (the main axis of the hyperbola).
- Here, \( a^2 = 4 \), so \( a = 2 \). - With the center of the hyperbola at (0, 0), which means the figure is symmetric about this point, the vertices are found at positions (+/-2, 0).So, the vertices are (2, 0) and (-2, 0). These tell us the hyperbola opens horizontally along the x-axis.
- Here, \( a^2 = 4 \), so \( a = 2 \). - With the center of the hyperbola at (0, 0), which means the figure is symmetric about this point, the vertices are found at positions (+/-2, 0).So, the vertices are (2, 0) and (-2, 0). These tell us the hyperbola opens horizontally along the x-axis.
Foci of a Hyperbola
Foci are crucial points that help to define the shape and orientation of a hyperbola. They lie on the transverse axis, further out than the vertices.Using the formula \( c^2 = a^2 + b^2 \), where \(a^2 = 4\) and \(b^2 = 4\), we can calculate:- \( c^2 = 4 + 4 = 8 \)- \( c = \sqrt{8} = 2\sqrt{2} \)Thus, the hyperbola's foci are at \((2\sqrt{2}, 0)\) and \((-2\sqrt{2}, 0)\).
These positions indicate that the foci are aligned along the x-axis, each positioned beyond a vertex, signaling that the hyperbola extends horizontally through these points.
These positions indicate that the foci are aligned along the x-axis, each positioned beyond a vertex, signaling that the hyperbola extends horizontally through these points.
Asymptotes of a Hyperbola
Asymptotes function like invisible guidelines that indicate the direction a hyperbola will approach as it stretches away from its center. They don't intersect the hyperbola but lead us in understanding its ultimate path.For a centered hyperbola like \( \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1 \), asymptotes are given by:\[ y = \pm \frac{b}{a} x \]Here, \( a = 2 \) and \( b = 2 \), so the equations for the asymptotes become:- \( y = x \)- \( y = -x \)These straight lines intersect at the origin (0, 0) and stretch diagonally across the plane, forming a cross-like structure. As the hyperbola curves closer, it approaches but never meets these lines.