Chapter 7: Problem 67
Give the focus, directrix, and axis of each parabola. $$x^{2}=16 y$$
Short Answer
Expert verified
Focus: (0, 4), Directrix: y = -4, Axis: x = 0.
Step by step solution
01
Identify the Parabola Form
The given equation is \(x^2 = 16y\), which matches the form \(x^2 = 4py\), where the parabola opens upwards or downwards. Here, \(x\) is squared, indicating a vertical axis of symmetry.
02
Determine the Focus
To find the focus, we need to find \(p\). Given \(x^2 = 4py\), we compare this with our equation \(x^2 = 16y\) and identify that \(4p = 16\). Solving for \(p\), we get \(p = 4\). Thus, the focus is located at \((0, p) = (0, 4)\).
03
Determine the Directrix
The directrix of a parabola is given by \(y = -p\). So with \(p = 4\), the equation of the directrix is \(y = -4\).
04
Identify the Axis of Symmetry
The axis of symmetry for a parabola in the form \(x^2 = 4py\) is the vertical line whose equation is \(x=0\). It is a vertical line along the \(y\)-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parabola
A parabola is a U-shaped curve that can open either upward or downward if it lies on a vertical axis or side-to-side along a horizontal axis. Parabolas are a type of conic section, which means they are formed by the intersection of a plane with a right circular cone. In the equation \(x^2 = 16y\), the parabola is said to be vertically oriented, as \(x\) is the squared variable, indicating that the parabola opens upwards or downwards.
Key properties of a parabola include:
Key properties of a parabola include:
- The vertex, which is the highest or lowest point on the parabola depending on its orientation.
- The axis of symmetry, which is a line that divides the parabola into two mirror-image halves.
- The focus and directrix, which help define the parabola's shape and position.
Focus and Directrix
The focus and directrix are crucial in defining the exact shape and position of a parabola. For the parabola \(x^2 = 16y\), determining these components relies on understanding the equation’s standard form. Here we have \(x^2 = 4py\), where \(p\) is a constant that helps locate both the focus and the directrix.
In this example, by comparing \(x^2 = 16y\) with \(x^2 = 4py\), we find that \(4p = 16\), hence \(p = 4\).
In this example, by comparing \(x^2 = 16y\) with \(x^2 = 4py\), we find that \(4p = 16\), hence \(p = 4\).
- The focus is a point on the interior of the parabola, and it is located at \((0, p)\), which means for our equation, the focus is at \((0, 4)\).
- The directrix is a horizontal line that lies outside the parabola, corresponding to \(y = -p\). In this case, the directrix is \(y = -4\).
Axis of Symmetry
The axis of symmetry of a parabola is a vertical or horizontal line that divides the parabolic curve into two equal halves, mirroring each other. This line passes through the vertex of the parabola and is a crucial part of the geometric structure.
For parabolas oriented vertically like \(x^2 = 16y\), the axis of symmetry is vertical. Specifically, it is the line \(x = 0\). This axis runs along the y-axis of the coordinate plane.
For parabolas oriented vertically like \(x^2 = 16y\), the axis of symmetry is vertical. Specifically, it is the line \(x = 0\). This axis runs along the y-axis of the coordinate plane.
- The axis of symmetry directly affects how the parabola is graphed. Knowing this line helps in perfectly sketching both sides of the parabola.
- It also determines the direction in which the parabola opens.