Download Section 2.2 part 2

Vocabulary for section 2.2
Part II
MA418
McAllister
Spring 2010
A few random terms
before we get started
• Parallel lines (rays, line segments) –
lines which lie in the same plane and
never intersect.
• Perpendicular lines – lines which
intersect to form 90 degree (or right)
angles.
• Adjacent vertices – vertices that are the
endpoints of one side of a polygon.
Classifying Polygons
– number of sides
•
•
•
•
•
•
3 – triangle
•
4- quadrilateral •
5 – pentagon
•
6 – hexagon
•
7 – heptagon
8 – octagon
9 - nonagon
10 – decagon
12 – dodecagon
N – N-gon
Classifying polygons
- by general characteristics
• Equilateral – all of the sides in the
figure are the same length.
• Equiangular – all of the angles in the
figure have the same measure.
• Regular – all of the sides are the
same length and all of the angles
have the same measure.
Special classifications for
specific shapes - TRIANGLES
• Acute – all three angles are less than 90
degrees
• Obtuse – one angle is between 90 and 180
degrees
• Right – one angle is exactly 90 degrees
• Scalene – all three sides (and angles) are
different measures
• Isosceles – at least (exactly) two sides are the
same length.
• Some triangles may have more than one of
these classifications.
Special classifications for
specific shapes - QUADRILATERALS
• Trapezoid – has at least (exactly) one pair of
parallel sides.
• Kite – has two pairs of adjacent, congruent
sides
• Parallelogram – has two pairs of parallel sides
• Rectangle – a parallelogram with at least one
right angle
• Rhombus – a parallelogram with all sides
congruent
• Square – a regular quadrilateral
Symmetries
– another way to classify figures
• Reflection symmetry – if there exist a line
along which the figure can be folded so
that one side matches up exactly with
the other side.
– This line is called the line of symmetry
or the axis of symmetry.
• Rotation symmetry - if the figure can be
turned around a point less than 360
degree and match up.
– This point is called the center of rotation.
Circles are not Polygons – but they are
very special
• Circle – all the given points equidistant from a
given point called the center.
• Radius – a line segment from the center of a
circle to a point on the circle.
• Diameter – a line segment that goes through the
center of the circle and has endpoints on the
circle.
• Circles are symmetrical around the center point
and reflective across any diameter.
Let’s explore these shapes
• Get out worksheet #12 – classify each
of the shapes on the page with all of
the terms in section 2.2 that we’ve
discussed. We’ll do one together.
• Let’s look at the following problems
from the book – p. 59, #7, 17