In this lesson you will identify and use properties
and relationships of plane geometry to describe shapes
and figures. You will also identify, describe, or draw
objects in the surrounding environment in geometric
terms.
Vocabulary:
If you need to check a word's definition, please go to the glossary by clicking the Vocabulary button
acute
angle
circumference
cone
cube
diagonal
diameter
edge
equilateral
face
hexagon
isosceles
obtuse
octagon
parallelogram
pentagon
perpendicular
pyramid
quadrilateral
rhombus
right angle
sphere
trapezoid
vertex (vertices)
cylinder
polyhedron
prism
Tips to Remember:
Symbols
To show a right
angle:
Hash marks may be used on line
segments to indicate that they are of equal length:
Theinverted Tis
used to indicate perpendicular lines.
Triangles
The measurement
of the three angles within a triangle total 180 degrees.
There are three kinds of triangles. An equilateral
triangle is a triangle that has all
three sides the same length. Anisosceles
triangle is a triangle that has two
sides that are the same length. A scalene
triangle is a triangle that has all
three sides with a different length.
Angles
There are three kinds of angles.
A right angle measures 90 degrees.
An acute angle measures less than 90
degrees. An obtuse angle measures greater
than 90 degrees.
Quadrilaterals
A quadrilateral is
a polygon with 4 sides. Some quadrilaterals include squares, rectangles, parallelograms,
and trapezoids.
Polygons
A polygon is a closed
figure formed by line segments.
A regular polygon is
a polygon with all sides the same length and the
all angles the same measure.
An irregular polygon is a polygon
with sides of different lengths and the angle measurements
are different as well.
Congruent Figures
Figures that have the same size
and shape.
Similar Figures
Figures that have the same shape,
but necessarily don't have the same size.
is
used to indicate perpendicular lines. 
