Chapter 12: Problem 37
\(29-40\) Find an equation for the parabola that has its vertex at the origin and satisfies the given condition(s). Focus on the positive \(x\) -axis, 2 units away from the directrix
Short Answer
Expert verified
The equation is \(x = \frac{1}{8}y^2\).
Step by step solution
01
Understanding the Problem
We need to find the equation of a parabola with the vertex at the origin. The condition given is that it is 2 units away from the directrix along the positive x-axis. This leads us to a parabola with a horizontal axis of symmetry.
02
Identifying the Directrix and Focus
For a parabola with a horizontal axis of symmetry and the vertex at the origin \((0,0)\), the equation is typically of the form \(x = \frac{1}{4p}y^2\), where \(p\) is the distance from the vertex to the directrix. Given that the directrix is 2 units away from the vertex, \(p = 2\).
03
Equation of the Parabola
Substitute \(p\) into the equation. Since the directrix is 2 units away on the negative x-axis (because we focus on the positive x-axis), the directrix is \(x = -2\), and the focus is at \((2,0)\). Thus, the equation of the parabola is \(x = \frac{1}{4p}y^2\) with \(p = 2\). This simplifies to \(x = \frac{1}{8}y^2\).
04
Final Equation
The equation of the parabola with the vertex at the origin and the given condition is \(x = \frac{1}{8}y^2\). The parabola opens to the right, as it is symmetric with respect to the positive x-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex at Origin
A parabola is a symmetrical curve shaped like an open bowl. When we say the "vertex at origin," it means the apex of this bowl is located at the point (0, 0) on a coordinate grid. The vertex is a critical part of the parabola because it is the point that is equally distant to all points on the parabola and its directrix.
- With the vertex at origin, other elements like the axis of symmetry, focus, and directrix are easily defined.
- This makes the calculations involving parabolas simpler because it eliminates the need for shifts in both x and y directions.
Focus and Directrix
Every parabola has a focus and a directrix, both playing a vital role in its structure. These two components help define the shape and orientation of the parabola. - **Focus:** It is a point from which distances are measured in forming the parabola. For a parabola with its vertex at the origin (0, 0) and a horizontal axis, the focus is located along the x-axis. If the focus is 2 units away along the positive x-axis, the position will be (2, 0).- **Directrix:** This is a line perpendicular to the axis of symmetry from which distances are calculated to form the parabola. For our specific case, the directrix is situated on the x-axis but is positioned opposite to the focus, at \( x = -2 \). The relationship between the focus and directrix allows us to derive the parabola's equation. A parabola is the set of all points equidistant from the focus and directrix.
Horizontal Axis of Symmetry
The axis of symmetry is an imaginary line that creates a mirror image of the parabola, ensuring one side is a reflection of the other. For a horizontal parabola, this axis is a horizontal line. It directly affects the parabola's opening, which in this scenario means it opens to the right.
- If the vertex is at the origin, the horizontal axis of symmetry lies along the x-axis.
- This makes horizontal parabolas open either to the right or the left. In this problem, it opens to the right because the focus is positioned along the positive x-axis.