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Geometry: Unit 3
A set of flashcards reviewing the keywords and concepts taught in Geometry Unit 3.
51
Mathematics
10th Grade
11/30/2010

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Cards

Term
a polygon with all angles congruent
Definition
equiangular polygon 
Term
a polygon with all sides congruent 
Definition
equilateral polygon 
Term
isosceles triangle 
Definition
a triangle with at least two congruent sides
Term
a triangle with three congruent sides
Definition
equilateral triangle 
Term
a triangle with no congruent sides
Definition
scalene triangle 
Term
a closed figure formed by three or more line segments in a plane, such that each line segment intersects exactly two other line segments at their endpoints only 
Definition
polygon
Term
An angle is formed by _____
Definition
two rays that have the same endpoints (called the vertex) and do not lie on the same line
Term

The four characteristics that a figure must have in order to qualify as a polygon include: 

- must have at least ____ sides

- the sides must be _____

- the sides can ____ only at their ____

- must be a _______ that lies flat on a plane 

Definition

- three

- straight 

- intersect; endpoints

- closed figure 

Term
an angle whose measure is 90 degrees
Definition
right angle
Term
an angle whose measure is less than 90 degrees 
Definition
acute angle
Term
an angle whose measure is greater than 90 degrees
Definition
obtuse angle
Term
an angle whose measure is 180 degrees
Definition
a straight line
Term

What polygon? 

Number of sides: 4

Definition
quadrilateral 
Term

What polygon? 

5 sides

Definition
pentagon
Term

What polygon? 

6 sides

Definition
hexagon
Term

What polygon? 

7 sides

Definition
heptagon
Term

What polygon? 

8 sides

Definition
octagon
Term

What polygon? 

9 sides

Definition
enneaon/nonagon
Term

What polygon? 

10 sides

Definition
decagon
Term
the center of a regular polygon is the point inside the polygon that is _______
Definition
equidistant from each vertex
Term
an angle formed by line segments drawn from the center of two consecutive vertices 
Definition
a central angle
Term
reflections, rotations, and translations are called ____ because they do not change the size or shape of a figure
Definition
isometric transformations
Term
a reflection is a ____
Definition
'flip' across a line
Term
a rotation is a ____
Definition
'turn' around a point
Term
a transformation is a ___
Definition
'slide' in one direction 
Term
All regular polygons have both ___ and ____ symmetry. 
Definition
reflection; rotation
Term
The number of lines of symmetry in a regular polygon is equal to ____. 
Definition
the number of sides
Term
The measure of the smallest angle by which a polygon can be rotated to look exactly like the original polygon is equal to _______. 
Definition
the measure of the central angle of the polygon 
Term

____ = 360 degrees

                       ¯n¯

 

n = number of sides

 

 

Definition
central angle
Term
a quadrilateral with two pairs of parallel sides
Definition
parallelogram
Term
a parallelogram with four congruent sides
Definition
rhombus
Term
a quadrilateral with exactly one pair of parallel sides 
Definition
Term
The _____ states that if you have a line and a point that is not on that line, then there is _____ through that point that is also parallel to the given line. 
Definition
Parallel Postulate; only one line 
Term
A horizontal line is flat so its steepness is ____
Definition
zero
Term
The slope of a vertical line is ____.
Definition
undefined
Term
Since parallel lines have the same steepness, they have the _____. 
Definition
same slope
Term
The _____ states that any two nonvertical lines are parallel if and only if _____. 
Definition
Parallel Lines Theorem; they have the same slope
Term
The Perpendicular Lines Theorem states that two coplanar nonvertical lines are perpendicular if and only if the product of their slopes equals ___. Any vertical line is ___ to any ____. 
Definition
-1; perpendicular; horizontal 
Term
The coordinates of the midpoint of the line segment with endpoints (x, y) and (x2, y2) are ____
Definition

      (x + x2)   (y + y2)

       ¯¯¯    ,     ¯¯¯

      2              2

Term
The ___ is a number that represents how steep the line is. 
Definition
slope of a line or line segment
Term
If the slope on a gridsystem goes up (increases) from left to right, then it is ____ -- if it decreases, or goes downhill, it is ____. 
Definition
positive; negative
Term
ratio of __ to ___ = slope
Definition
rise;  run
Term

              m = rise      = ___

      ¯¯¯

       run 

Definition

y2 - y1

¯¯¯¯¯

x2 - x1

Term
A midsegment is the segment that joins the midpoints of _____. 
Definition
the legs of a triangle
Term
Every triangle has __ bases and ___ midsegments -- each midsegment joins the midpoints of two sides. 
Definition
three; three
Term

According to the Triangle Midsegment Theorem, for any triangle: 

1. The length of a midsegment is equal to ____ the length of its corresponding base. 

2. A midsegment is ____ to its corresponding base. 

Definition

one-half 

parallel 

Term
The perimeter of the triangle formed by the midsegments is equal to ___ the perimeter formed by the vertices of the original triangle. 
Definition
one-half
Term
A ____ passes through the midpoint of a line segment and divides it into two congruent line segments. 
Definition
segment bisector
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