Geometry Ch 3: Symmetry
What shapes lines of symmetry equal the number of sides?
Polygons: octagons, hexagon and pentagon
How many lines of symmetry are their in a parallelogram?
0
How many lines of symmetry are there in a quadrilateral with four different side lengths?
0
How many lines of symmetry are there in a scalene triangle?
0
How many lines of symmetry are their in a isosceles trapezoid?
1
How many lines of symmetry are their in a kite?
1
How many lines of symmetry are there in an isosceles triangle?
1
How many lines of symmetry are their in a rectangle?
2
How many lines of symmetry are their in a rhombus?
2
How many lines of symmetry are there in an equilateral triangle?
3
How many lines of symmetry are their in a square?
4
How many lines of symmetry are their in a regular pentagon?
5
How many lines of symmetry are their in a regular hexagon?
6
How many lines of symmetry are their in a regular octagon?
8
What is the relationship between the angle of rotation and the order of symmetry?
An order n corresponds to a 360/n angle of rotation
How many lines of symmetry are their in a circle?
Infinitely many
Order 1 of rotational symmetry (trapezoid)
NO rotational symmetry
Order 5 of rotational symmetry (regular pentagon)
Spin a regular pentagon on its center point and every 72 degrees it will appear unchanged
How many lines of symmetry are their in a non-isosceles trapezoid?
0
Order 3 of rotational symmetry (equilateral triangle)
Spin the equilateral triangle on the center point and every 120 degrees it will appear unchanged
Order 2 of rotational symmetry (parallelogram)
Spin the parallelogram about the center point 180 degrees and it will appear unchanged
Order 4 of rotational symmetry (square)
Spin the square about the center point 90 degrees and it will appear unchanged
Order of Symmetry
The number of positions in which the rotated object appears unchanged
Center of Rotation
The point around which the figure is rotated(rotational symmetry)
Line Symmetry
a line that divides a figure into two mirror images. The figure is mapped onto itself by reflection in this line.
What is another description for point symmetry?
rotational symmetry of 180degrees
Angle of rotation
the smallest angle needed for the "spin" (rotational symmetry)
Point Symmetry
when a figure looks the same when up-side down,(rotated 180 degrees) as it does right-side up
rotational symmetry
when rotating the figure around a center point by less than 360 degrees, the figure appears unchanged
