Translation Transform
Given a vector V and a point P. A vector can be specified by its direction and length. Translation (often a parallel translation) P' of P by V is the point such that PP' equals the vector V. In other words, P' is located at the distance from P equal to the length of V and in the same direction.
P' exists for any P. Let's write
T_{V}T_{-V} = I, |
where I is the identity transform. If V is a non-zero vector the for no point
The translation transform T_{V} applies to arbitrary shapes point-by-point. Each point of a given shape S is translated by V, and the collection of these translations is the translated image of S:
On the other hand, if S' is known to be a translated image of S, then for any points P and Q in S,
In the applet, you can create polygons with a desired number of vertices, drag the vertices one at a time, or drag the polygon as a whole. Vectors of translations can also be dragged. They rotate if dragged near their endpoints, or translate if dragged nearer their midpoint.
What if applet does not run? |
The following observations are noteworthy:
Translation preserves the orientation. For example, if a polygon is traversed clockwise, its translated image is likewise traversed clockwise.
Translation is isometry: a translation preserves distances.
Translation preserves angles.
Translation maps parallel lines onto parallel lines and, moreover, a line and its image are also parallel.
Except for the trivial translation by a zero vector, translation have no fixed points. All lines parallel to the vector of a translation are fixed by the translation.
Successive translations result in a translation. Moreover,
T_{V}T_{U} = T_{V+U}.
The order of translations does not matter: any two translations commute. In fact, for two vectors U and V,
T_{U}T_{V} = T_{V}T_{U}.
Here is a list of several problems that are solved with the help of translation:
- A Property of Rhombi
- A Property of the Line IO
- Bottles in a Wine Rack
- Building a Bridge
- Building Bridges
- Circles with Equal Collinear Chords
- Find a Common Chord of Given Length
- Join Circles by Given Segment
- Translated Triangles
Geometric Transformations
- Plane Isometries
- Plane Isometries As Complex Functions
- Affine Transformations (definition)
- Inversion
- Projective transformation (definition)
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Copyright © 1996-2017 Alexander Bogomolny
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