Chapter 13: Problem 10
Find the image of the rectangle with the given corners and find the Jacobian of the transformation. \(x=u, y=u^{2}-v^{2} ;(0,0),(3,0),(3,1),(0,1)\)
Short Answer
Expert verified
Images: (0,0), (3,9), (3,8), (0,-1). Jacobian determinant: \(-2v\).
Step by step solution
01
Understanding the Transformation
We have the transformation given by the equations \( x = u \) and \( y = u^2 - v^2 \). This means that for a given point \((u, v)\) in the parameter space, the point \((x, y)\) can be calculated using these equations.
02
Determine Image of Corner (0,0)
For corner \((u, v) = (0, 0)\), we substitute into the transformation equations: \( x = 0 \) and \( y = 0^2 - 0^2 = 0 \). Thus, the image is \((0, 0)\).
03
Determine Image of Corner (3,0)
For corner \((u, v) = (3, 0)\), we substitute into the transformation equations: \( x = 3 \) and \( y = 3^2 - 0^2 = 9 \). Thus, the image is \((3, 9)\).
04
Determine Image of Corner (3,1)
For corner \((u, v) = (3, 1)\), we substitute into the transformation equations: \( x = 3 \) and \( y = 3^2 - 1^2 = 8 \). Thus, the image is \((3, 8)\).
05
Determine Image of Corner (0,1)
For corner \((u, v) = (0, 1)\), we substitute into the transformation equations: \( x = 0 \) and \( y = 0^2 - 1^2 = -1 \). Thus, the image is \((0, -1)\).
06
Find the Jacobian
To find the Jacobian of the transformation, calculate the matrix of partial derivatives:\[J = \begin{bmatrix} \frac{\partial x}{\partial u} & \frac{\partial x}{\partial v} \ \frac{\partial y}{\partial u} & \frac{\partial y}{\partial v} \end{bmatrix} = \begin{bmatrix} 1 & 0 \ 2u & -2v \end{bmatrix}\]
07
Calculate the Determinant of the Jacobian
The determinant of the Jacobian matrix is:\[\text{det}(J) = \left(1 \cdot (-2v) - (0 \cdot 2u)\right) = -2v\]Thus, the Jacobian determinant is \(-2v\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Jacobian Matrix
The Jacobian matrix is a fundamental structure in calculus, specifically in the context of transformations. It helps us understand how a transformation affects areas or volumes locally around a point. In our exercise, the transformation is given by the equations:
- \( x = u \)
- \( y = u^2 - v^2 \)
- \( \frac{\partial x}{\partial u} = 1 \), \( \frac{\partial x}{\partial v} = 0 \)
- \( \frac{\partial y}{\partial u} = 2u \), \( \frac{\partial y}{\partial v} = -2v \)
Determinant Calculation
The determinant of the Jacobian matrix provides insight into how the transformation scales area locally. Specifically, it tells us how the area around a point in the parameter space is stretched or shrunk when mapped to the image space.
For the given transformation, the determinant is calculated from the Jacobian matrix:
For the given transformation, the determinant is calculated from the Jacobian matrix:
- Jacobian matrix: \( J = \begin{bmatrix} 1 & 0 \ 2u & -2v \end{bmatrix} \)
- Determinant formula: \( \text{det}(J) = (1)(-2v) - (0)(2u) = -2v \)
Image of Transformation
Finding the image of a transformation involves mapping specified points in one space (like a plane or rectangle) to another using transformation equations. In this exercise, we've provided four corners of a rectangle defined by parameter coordinates:\( (0,0), (3,0), (3,1), (0,1) \). To find the image in the \(x, y\) space:
- Corner \((0, 0)\) is mapped to \((0, 0)\).
- Corner \((3, 0)\) is mapped to \((3, 9)\).
- Corner \((3, 1)\) is mapped to \((3, 8)\).
- Corner \((0, 1)\) is mapped to \((0, -1)\).