Change of Coordinate Systems

From Math Images

(Difference between revisions)
Jump to: navigation, search
Line 5: Line 5:
|ImageDescElem=It is a common practice in mathematics to use different coordinate systems to solve different problems. An example of a switch between coordinate systems follows: suppose we take a set of points in regular x-y '''Cartesian Coordinates''', represented by ordered pairs such as (1,2), then multiply their x-components by two, meaning (1,2) in the old coordinates is matched with (2,2) in the new coordinates.
|ImageDescElem=It is a common practice in mathematics to use different coordinate systems to solve different problems. An example of a switch between coordinate systems follows: suppose we take a set of points in regular x-y '''Cartesian Coordinates''', represented by ordered pairs such as (1,2), then multiply their x-components by two, meaning (1,2) in the old coordinates is matched with (2,2) in the new coordinates.
-
Under this transformation, a set of points would become stretched in the horizontal x-direction since each point becomes further from the vertical y-axis (except for points originally on the y-axis, which remain on the axis). A set of points that was originally contained in a circle in the old coordinates would be contained by a stretched-out ellipse in the new coordinate system, as shown in this page's main image.
+
Under this transformation, a set of points would become stretched in the horizontal x-direction since each point becomes further from the vertical y-axis (except for points originally on the y-axis, which remain on the axis). A set of points that was originally contained in a circle in the old coordinates would be contained by a stretched-out ellipse in the new coordinate system, as shown in the top two figures of this page's main image.
Many other such transformations exist and are useful throughout mathematics, such as mapping the points in a disk to a rectangle.
Many other such transformations exist and are useful throughout mathematics, such as mapping the points in a disk to a rectangle.
-
|ImageDesc= Some of these mappings can be neatly represented in matrix notation, in the form
+
|ImageDesc= Some of these mappings can be neatly represented by [[vectors]] and matrices, in the form
<math> A\vec{x}=\vec{x'} </math>
<math> A\vec{x}=\vec{x'} </math>
-
Where <math> \vec{x}</math> is the coordinate [[vector]] of our point in the original coordinate system and <math> \vec{x'} </math> is the coordinate vector of our point in the new coordinate system.
+
Where <math> \vec{x}</math> is the <balloon title="A vector for which each components represents a coordinates">coordinate vector</balloon> of our point in the original coordinate system and <math> \vec{x'} </math> is the coordinate vector of our point in the new coordinate system.
For example the transformation in the basic description, doubling the value of the x-coordinate, is represented in this notation by
For example the transformation in the basic description, doubling the value of the x-coordinate, is represented in this notation by

Revision as of 11:24, 12 June 2009

Image:inprogress.png

Change of Coordinates

The same object, here a circle, can look completely different depending on which coordinate system is used.


Basic Description

It is a common practice in mathematics to use different coordinate systems to solve different problems. An example of a switch between coordinate systems follows: suppose we take a set of points in regular x-y Cartesian Coordinates, represented by ordered pairs such as (1,2), then multiply their x-components by two, meaning (1,2) in the old coordinates is matched with (2,2) in the new coordinates.

Under this transformation, a set of points would become stretched in the horizontal x-direction since each point becomes further from the vertical y-axis (except for points originally on the y-axis, which remain on the axis). A set of points that was originally contained in a circle in the old coordinates would be contained by a stretched-out ellipse in the new coordinate system, as shown in the top two figures of this page's main image.

Many other such transformations exist and are useful throughout mathematics, such as mapping the points in a disk to a rectangle.

A More Mathematical Explanation

Some of these mappings can be neatly represented by vectors and matrices, in the form

UNIQ682a [...]

Some of these mappings can be neatly represented by vectors and matrices, in the form

 A\vec{x}=\vec{x'}

Where  \vec{x} is the coordinate vector of our point in the original coordinate system and  \vec{x'} is the coordinate vector of our point in the new coordinate system.

For example the transformation in the basic description, doubling the value of the x-coordinate, is represented in this notation by

\begin{bmatrix}

2 & 0  \\
0 & 1  \\
\end{bmatrix}\vec{x} = \vec{x'}

As can be easily verified.

The ellipse that is tilted relative to the coordinate axes is created by a combination of rotation and stretching, represented by the matrix

\begin{bmatrix}

2cos(\theta) & -sin(\theta)\\
2sin(\theta) & cos(\theta)  \\
\end{bmatrix}\vec{x} = \vec{x'}

Some very useful mappings cannot be represented in matrix form, such as mapping points from Cartesian Coordinates to Polar Coordinates. Such a mapping, as shown in this page's main image, can map a disk to a rectangle. Each origin-centered ring in the disk consists of points at constant distance from the origin and angles ranging from 0 to  2\pi . These points create a vertical line in Polar Coordinates. Each ring at a different distance from the origin creates its own line in the polar system, and the collection of these lines creates a rectangle.

The transformation from Cartesian coordinates to Polar Coordinate can be represented algebraically by



\begin{bmatrix}
r\\
\theta\\
\end{bmatrix}
=
\begin{bmatrix}
\sqrt{x^2 + y^2}\\
\arctan{y/x}\\
\end{bmatrix}




Teaching Materials

There are currently no teaching materials for this page. Add teaching materials.









If you are able, please consider adding to or editing this page!

Have questions about the image or the explanations on this page?
Leave a message on the discussion page by clicking the 'discussion' tab at the top of this image page.






Personal tools