Chapter 12: Problem 8
In Exercises \(1-16,\) give a geometric description of the set of points in space whose coordinates satisfy the given pairs of equations. $$y^{2}+z^{2}=1, \quad x=0$$
Short Answer
Expert verified
The solution represents a circle of radius 1 in the yz-plane centered at the origin.
Step by step solution
01
Understanding the First Equation
The first equation is \( y^2 + z^2 = 1 \). This represents a circle in the \( yz \)-plane with a center at \((0, 0)\) and a radius of 1.
02
Understanding the Second Equation
The second equation is \( x = 0 \), which represents the \( yz \)-plane in three-dimensional space. This means all points satisfying this condition lie on the plane where \( x \) coordinate is zero.
03
Combining the Conditions
Since \( x = 0 \) restricts us to the \( yz \)-plane, and \( y^2 + z^2 = 1 \) describes a circle within this plane, combining these conditions, we have a circle of radius 1 centered at \((0,0,0)\) on the \( yz \)-plane.
04
Geometric Description
The set of points satisfying both equations is a vertical circle in the \( yz \)-plane with a radius of 1. This circle is centered at the origin \((0, 0, 0)\) in three-dimensional space.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Circle in 3D space
In coordinate geometry, a circle can be understood as a set of all points that are equidistant from a single point, known as the center. When visualizing this in three-dimensional space, a circle can occupy any plane – the challenge is just to define it clearly in terms of the axes. Let’s break it down further:
- The circle’s general equation is given by \[ (y - a)^2 + (z - b)^2 = r^2, \]representing a circle with center \((a, b)\) and radius \(r\) in the yz-plane.
- When this circle is situated in 3D space, to anchor it, you must define a fixed plane – for example, the equation \(x = c\), holds all points of the circle in a plane parallel to the yz-plane.
- In the given exercise, \(y^2 + z^2 = 1\) signifies that the circle has a center at the origin, \((0,0)\) in the yz-plane, and a radius 1.
- Consequently, the circle sits vertically on the yz-plane in three-dimensional space, having the x-coordinate fixed at zero.
Geometric description
Understanding geometry in three-dimensional space often involves visualizing shapes that you've encountered in two dimensions. The trick is to imagine how these shapes, like circles, exist and align in 3D. Let's have a look at how you might describe this geometrically:
- For any shape, the geometric description often begins with its defining equations. For the circle in question, \(y^2 + z^2 = 1\) tells us the shape of what we see in the yz-plane.
- This equation reveals a circle in the yz-plane, meaning all its points meet the criteria of being equidistant from the center (0,0) with a common radius, here being 1.
- Next, \(x=0\) situates this circle within the yz-plane at the origin (0,0,0) in 3D space.
- Therefore, the geometric description, harmonizing both equations, is a vertical circle based in the yz-plane with its center situated at the 3-dimensional origin.
Planes in space
Planes in 3D space are flat, two-dimensional surfaces that extend infinitely within three-dimensional coordinate systems. They are primarily defined using linear equations and can be aligned with or intersect the axes. Here’s how they function conceptually:
- A plane can be represented as \(Ax + By + Cz = D\), where \(A, B,\) and \(C\) are the coefficients indicating the orientation of the plane.
- When dealing with planes that are parallel to a particular axis, such as the yz-plane, the equation simplifies to \(x = c\) where \(c\) is a constant.
- In our context, \(x = 0\) is such a plane, serving as the yz-plane itself. This implies all points on this plane have an x-coordinate of zero.
- Being able to recognize these planes helps significantly when situating other geometries like circles within the larger three-dimensional space.