Notes for 4­20 Lesson_2_Inv_1_Symmetries.notebook
April 28, 2011
IM1 - 4/20/11
Learning Target: Symmetries of a Polygon
If a gallon of paint covers 450 ft2, how
many gallons must you buy to apply two
coats to seven rectangular walls, each
of which is 12 ft by 8 ft?
Apr 19­7:51 AM
1
Notes for 4­20 Lesson_2_Inv_1_Symmetries.notebook
April 28, 2011
Unit 6 Notes Continued:
Regular Polygon - a polygon with congruent
sides and congruent angles
Rectangle - a quadrilateral with four right
angles and opposite sides congruent
Rhombus - a quadrilateral with four
congruent sides and opposite angles congruent
Kite - a quadrilateral that has adjacent sides
congruent, it's diagonals are perpendicular to
each other
Apr 19­7:55 AM
2
Notes for 4­20 Lesson_2_Inv_1_Symmetries.notebook
April 28, 2011
Symmetries in a Polygon
Central Angle of a Polygon - the angle that is
formed from the center of a regular polygon
to two of its vertices
Find the measure of the
central angle in each shape
What is the formula for finding the central
angle of a regular n-gon?
Apr 19­8:20 AM
3
Notes for 4­20 Lesson_2_Inv_1_Symmetries.notebook
April 28, 2011
Rotational Symmetry - if a polygon can be
rotated by a certain degree and still coincide
with the original figure
Note: these are all regular polygons
Triangle
Square
Pentagon
Hexagon
Heptagon
Octagon
Central Angle
Rotational Symmetries
Central Angle
Rotational Symmetries
How many rotational symmetries will an
n-gon have?
Apr 19­9:53 AM
4
Notes for 4­20 Lesson_2_Inv_1_Symmetries.notebook
April 28, 2011
Reflection/Line Symmetry - if a figure can
be reflected over a line where one half of
the figure will coincide with the other half,
it has reflection symmetry
How many lines of symmetry will any regular
n-gon have?
Where do the lines of symmetry cut the
shape when it has an even number of sides?
Where do the lines of symmetry cut the
shape when it has an odd number of sides?
Apr 19­8:20 AM
5