Download Week of Feb. 19

Congruent Triangles
Introduction to
congruent angles
Polygon
• a closed plane figure
formed by three or more
segments that do not cross
Congruent
• having the same size or
angle measure.
• The symbol for congruent is 
So, the symbol,  stands for
“is congruent to.”
Congruent Polygons
• polygons with the same
size AND shape.
C
A
 CAB   FGE
B
E
F
G
Corresponding Parts
• parts of polygons that are
matching and congruent.
FEG
FG CBA   ___
CA  ____
F
C
A
B
E
G
Need to Know!
**When stating congruent
sides, the order that the
segments are written in is
very important, because it
will identify direction.
Polygons and
Quadrilaterals
What are the
differences?
Quadrilateral
• a FOUR sided polygon.
Name some quadrilaterals?
Square
Rectangle
Rhombus/ Diamond
Parallelogram
Trapezoid
Pentagon
• a FIVE sided polygon.
What famous building houses
the various armed forces?
The Pentagon
Hexagon
• a SIX sided polygon.
Octagon
• an EIGHT sided polygon.
Name a common object that
has this shape.
stop sign
Decagon
• a TEN sided polygon.
Regular Polygon
• a polygon with ALL sides
congruent and ALL angles
congruent.
Name a regular polygon that is:
a triangle – Equilateral Triangle
a quadrilateral – Square
Parallel Lines
• two lines that lie in the same
plane (a flat surface) and
DO NOT intersect
Trapezoid
 quadrilateral with exactly
one pair of parallel sides
Parallelogram
• quadrilateral with both pairs
of opposite sides parallel
Rectangle
• a parallelogram with 4 right
angles
Rhombus
• a parallelogram with 4
congruent sides
Square
• a parallelogram with 4 right
angles and 4 congruent sides
What other names can a square have?
quadrilateral
parallelogram
rectangle
rhombus
Can a rectangle be a square?
Yes, but not always.
When?
Only if all 4 sides are also
congruent.
Can a rhombus be a square?
Yes, but not always
When?
if all 4 angles are right
angles.
Can a trapezoid be a rectangle?
NO
Why?
Trapezoid can have only 1
set of parallel sides.
Rectangle has 2.
Is a rectangle always a
parallelogram?
Yes, by its definition.
a parallelogram with 4 right
angles
Is a square always a rectangle?
Yes, ALWAYS!
It fits the definition of a
rectangle because a square
is a parallelogram, and has
4 right angles.
Is a rectangle always a square?
NO
Only if the rectangle also
has 4 congruent sides.
Diagonal
• the segment that connects two
corners of a polygon, but does
not make a side of the
polygon.
• diagonals connect the inside of
a polygon
Circles
Almost there…
Circle
• the set of points in a plane
that are all the same
distance from a given point,
called the center.
• a circle is named by its
center
Radius
• a segment from the center
of a circle to a point on the
circle.
• The plural form of radius is
radii.
Diameter
• a segment that passes
through the center of a
circle and has both
endpoints on the circle.
Chord
• a segment that has both
endpoints on the circle.
Central Angle
• an angle with its vertex at
the center of a circle.
Arc
• a part of a circle (along the
outside of the circle)
• named using just 2 letters
Semicircle
• a half of a circle.
• named using 3 letters
–Why 3 letters?
Compass
• a geometric tool used to
draw circles and arcs.
Inscribed Polygon
• a polygon whose sides are
chords of a circle.
A chord is always a diameter.
True or False?
FALSE!
not always, a chord IS a
diameter, IF, it also passes
through the center of the
circle
A diameter is always chord.
True or False?
TRUE!
by definition, a diameter has
two endpoints on the circle.
A diameter is equal, in length,
to two radii.
True or False?
TRUE!
diameter is equal to the
radius times 2.
A radius can be a chord.
True or False?
FALSE!
only 1 part of a radius
touches the circle, not two
endpoints.
Identify!
C
D
B
A
G
F
E