| Vocabulary |
[Back] |
Kaleidoscopes, Hubcaps & Mirrors
| Congruent Figures | Two
figures are congruent if one is an image of the other under a reflection,
rotation, translation
or some combination of these transformations.
Put more simply, two figures are congruent if you can flip, turn, or slide
one figure so that it fits exactly on the other.
|
| Line
Reflection
FLIP |
a
transformation that matches each point on a
figure with its mirror image over (i.e. flipped across) a line.
click the icon for NVLM's line reflection activity
|
Reflectional
Symmetry |
a
figure or design has reflectional symmetry if you can draw a line that
divides the figure into halves that are mirror images. The line that
divides the figure into halves is called the line of symmetry.
|
| Rotation
TURN |
a
transformation that turns
a figure counterclockwise about a point.
|
| Rotational
Symmetry
|
a
figure or design has rotational symmetry if it can be rotated less than
one
full turn about a point to a position in which it looks the same as the
original.
click the icon for NVLM's rotation activity |
| Symmetry
|
An
object or design has symmetry if part of it is repeated to create a
balanced pattern. Three types of symmetry are reflectional
symmetry, rotational symmetry
and translational symmetry.
|
| Tessellation
|
A
design made from copies of a basic design element that cover a surface
without gaps or overlaps. Tessellations have translational
(slide) symmetry.
|
| Transformation | A
geometric operation that matches each point on a figure with an image
point. Line reflections, rotations
and translations are symmetry transformations.
|
| Translation
SLIDE |
a
transformation that slides each
point on a figure to an image point a given distance and direction from
the original point.
click the icon for NVLM's translation activity
|
| Translational
Symmetry
|
A
design has translational symmetry if it can be created by copying and
sliding a basic shape in a regular pattern. Translational symmetry
is often found in wallpaper designs and other tesselations. |
