Chapter 13: Problem 54
Equations of planes Find an equation of the following planes. The plane containing the z-axis and the point \(P_{0}(3,-1,2)\)
Short Answer
Expert verified
Answer: The equation of the plane containing the z-axis and the point \(P_{0}(3, -1, 2)\) is \(x + 3y = 6\).
Step by step solution
01
Find a vector in the xy-plane that is parallel to the plane
Since the plane contains the z-axis, its normal vector will have a z-component of 0. This means that the normal vector will lie in the xy-plane. Let's assume the normal vector to be \(\vec{n} = (A, B, 0)\). We don't know the values of A and B yet.
02
Find a vector from the origin to the point Pâ‚€
We are given a point \(P_{0}(3, -1, 2)\). We need to find a vector from the origin O(0, 0, 0) to this point. This can be found by subtracting the coordinates of the origin from the coordinates of the point \(P_{0}\):
\(\vec{OP_{0}} = P_{0} - O = (3 - 0, -1 - 0, 2 - 0) = (3, -1, 2)\)
03
Find the normal vector using dot product
The normal vector \(\vec{n}\) is perpendicular to the vector \(\vec{OP_{0}}\). The dot product of two perpendicular vectors is 0. So, we can find the normal vector by setting the dot product of \(\vec{n}\) with \(\vec{OP_{0}}\) equal to 0:
\(\vec{n} \cdot \vec{OP_{0}} = A(3) + B(-1) + 0(2) = 0\)
This equation describes a family of vectors in the xy-plane. We can simplify this equation to find the normal vector:
\(3A - B = 0\) (1)
Let's assume A = 1 for simplicity. Then, according to equation (1), B = 3. Therefore, the normal vector is:
\(\vec{n} = (1, 3, 0)\)
04
Find the equation of the plane
Now that we have the normal vector \(\vec{n} = (1, 3, 0)\) and a point \(P_{0}(3, -1, 2)\), we can find the equation of the plane. The equation of a plane given its normal vector \(\vec{n} = (A, B, C)\) and a point \(P_{0}(x_{0}, y_{0}, z_{0})\) in the plane is:
\(A(x - x_{0}) + B(y - y_{0}) + C(z - z_{0}) = 0\)
Plugging in the values for \(\vec{n}\) and \(P_{0}\), we get:
\(1(x - 3) + 3(y - (-1)) + 0(z - 2) = 0\)
Simplify the equation:
\(x - 3 + 3y + 3 = 0\)
Therefore, the equation of the plane containing the z-axis and the point \(P_{0}(3, -1, 2)\) is:
\(x + 3y = 6\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vector in Cartesian Coordinate System
along the x-axis, \( y \) along the y-axis, and \( z \) along the z-axis. These components specify the vector's direction and how far it extends in 3D space from the origin. In the plane equation problem, \( \vec{OP_{0}} = (3, -1, 2) \) represents the vector from the origin \( O(0, 0, 0) \) to the point \( P_{0}(3, -1, 2) \) on the plane.
Understanding vectors in Cartesian coordinates is fundamental for many geometrical calculations, providing a systematic way of describing positions and directions in space.
Understanding vectors in Cartesian coordinates is fundamental for many geometrical calculations, providing a systematic way of describing positions and directions in space.
Dot Product of Vectors
The dot product, also known as the scalar product, is an algebraic operation that takes two equal-length sequences of numbers (usually coordinate vectors) and returns a single number. This operation is denoted by \( \vec{u} \cdot \vec{v} \) for two vectors \( \vec{u} \) and \( \vec{v} \) and is calculated as \( (u_{1}v_{1} + u_{2}v_{2} + u_{3}v_{3}) \) in three-dimensional space.
The result of a dot product can tell us if two vectors are orthogonal (perpendicular), as orthogonal vectors have a dot product of zero. This property is crucial when determining the normal vector \( \vec{n} \) to a plane, as seen in the exercise, where \( \vec{n} \cdot \vec{OP_{0}} = 0 \) was used to formulate the characteristic relationship.
The result of a dot product can tell us if two vectors are orthogonal (perpendicular), as orthogonal vectors have a dot product of zero. This property is crucial when determining the normal vector \( \vec{n} \) to a plane, as seen in the exercise, where \( \vec{n} \cdot \vec{OP_{0}} = 0 \) was used to formulate the characteristic relationship.
Normal Vector to a Plane
A normal vector to a plane is a vector that is perpendicular to that plane. The defining property of the normal vector \( \vec{n} \) is that it should be orthogonal to any vector that lies on the plane, making it a fundamental element in describing the plane's orientation in space.
In the context of the given exercise, the normal vector \( \vec{n} = (1, 3, 0) \) was identified because it is orthogonal to vector \( \vec{OP_{0}} \) that lies on the plane. Determining the normal vector is a critical step in finding the equation of a plane, as the vector's components directly contribute to the plane's standard form equation.
In the context of the given exercise, the normal vector \( \vec{n} = (1, 3, 0) \) was identified because it is orthogonal to vector \( \vec{OP_{0}} \) that lies on the plane. Determining the normal vector is a critical step in finding the equation of a plane, as the vector's components directly contribute to the plane's standard form equation.
Equation of a Plane in Three-Dimensional Space
The equation of a plane in three-dimensional space can be determined if you know a point \( P_{0}(x_{0}, y_{0}, z_{0}) \) that lies on the plane and a normal vector \( \vec{n} = (A, B, C) \) to the plane. The general form of the plane equation is \( A(x - x_{0}) + B(y - y_{0}) + C(z - z_{0}) = 0 \) where the normal vector's components and the known point's coordinates are substituted in.
From the exercise, using the normal vector \( \vec{n} = (1, 3, 0) \) and the point \( P_{0}(3, -1, 2) \) on the plane, the equation \( x + 3y = 6 \) defines the plane. This concise equation allows us to understand the spatial relationship of any point relative to the plane and is a direct result of the normal vector properties and the specific point through which the plane passes.
From the exercise, using the normal vector \( \vec{n} = (1, 3, 0) \) and the point \( P_{0}(3, -1, 2) \) on the plane, the equation \( x + 3y = 6 \) defines the plane. This concise equation allows us to understand the spatial relationship of any point relative to the plane and is a direct result of the normal vector properties and the specific point through which the plane passes.