Chapter 7: Problem 26
In Problems \(23-28,\) use the discriminant to identify the conic without actually graphing. $$ x^{2}+\sqrt{3} x y-\frac{1}{2} y^{2}=0 $$
Short Answer
Expert verified
The conic is a hyperbola.
Step by step solution
01
Recall the General Form of a Conic Section
The general form for conic sections is given by the equation: \[ Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 \] Identify the coefficients: - \( A = 1 \) - \( B = \sqrt{3} \) - \( C = -\frac{1}{2} \)
02
Determine the Discriminant
The discriminant \( \Delta \) for a conic section is calculated as \[ \Delta = B^2 - 4AC \] Substitute the values we found:\[ \Delta = (\sqrt{3})^2 - 4 \cdot 1 \cdot \left(-\frac{1}{2}\right) \] \[ \Delta = 3 + 2 = 5 \]
03
Interpret the Discriminant
The value of the discriminant \( \Delta \) determines the type of conic section:- \( \Delta < 0 \): ellipse- \( \Delta = 0 \): parabola- \( \Delta > 0 \): hyperbolaSince \( \Delta = 5 > 0 \), the conic is a hyperbola.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Discriminant of Conic Sections
In the study of conic sections, the discriminant plays a crucial role in determining the nature of the conic without having to graph it. For an equation to be considered in the form of a conic, it should be expressed as: \[ Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 \] where \(A\), \(B\), \(C\), \(D\), \(E\), and \(F\) are constants. A vital part of this equation is the discriminant \( \Delta \), which is determined using the following formula: \[ \Delta = B^2 - 4AC \] The discriminant offers insights into the conic's geometric nature based on the relationships among the coefficients:
- \( \Delta < 0 \): Indicative of an ellipse, suggesting that the conic may take a circular or elliptical shape based on \(A\) and \(C\).
- \( \Delta = 0 \): Represents a parabola, characterized by its unique U-shape, either opening along the x-axis or y-axis.
- \( \Delta > 0 \): Identifies a hyperbola, which consists of two disconnected curves mirroring one another.
Types of Conics
Conics represent a fascinating group of curves generated by intersecting a plane with a double-napped cone. When classified based on their discriminant, they help reveal the nature of the intersection:
- Circle: A special case of an ellipse where the plane cuts perpendicular to the cone's axis, yielding a perfectly symmetric shape.
- Ellipse: Formed when a tilted plane intersects the cone at an angle, not parallel to the base, resulting in an oval shape. An ellipse occurs when \( \Delta < 0 \).
- Parabola: Occurs when the intersecting plane is parallel to the slant edge of the cone, creating a distinct U-shaped curve, with characteristics determined by \( \Delta = 0 \).
- Hyperbola: Takes form when the plane cuts both nappes of the cone, producing two symmetric, open curves. Identified by \( \Delta > 0 \), as in our example problem.
Hyperbola Identification
Identifying a hyperbola among conic sections can be achieved quickly by understanding its unique properties. Comprising two mirrored curves, a hyperbola is discovered using the discriminant: \(\Delta = B^2 - 4AC > 0\) An important feature of a hyperbola is that it's represented by equations where both quadratic terms \(Ax^2\) and \(Cy^2\) have opposing signs. This results in the conic intersecting the plane at an angle that exposes both cones. Understanding the geometry:
- A hyperbola can appear horizontally or vertically, contingent upon the signs and magnitudes of \(A\) and \(C\).
- Its standard equations vary:
- Horizontal hyperbola: Difference between squares: \(\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1\)
- Vertical hyperbola: Reversed equation: \(\frac{y^2}{a^2} - \frac{x^2}{b^2} = 1\)
- The foci are located outside its vertices, and the hyperbola opens around these foci, emphasizing the space between its branches.