Vertex
the point where two lines, line segments, or rays meet to form an angle Point A is a vertex for the angles formed.
A
measure of an arc
The degree measure of an arc is equal to the measure of its central angle.
0
0
75
75
m ACB
mAB
C
BA
Diagonal
Line segment that joins two vertices of a polygon, but is not a side of the polygon
Diagonals
bisect
To divide into two equal parts, cut in halfGI bisects FGH
means that
m FGI = m HGI
C
A B
D
EG
F
H
I
DE bisects AB
means that
C is the midpoint of AB
and AC=CB
GI bisects FGH
means that
m FGI = m HGI
Central angle
Angle in a circle with its vertex at the center of the circle
B
CA
ABC is a central angle.
Vertical angles The opposite angles formed when two
lines intersect
1 432
1 and 3 are vertical angles.
2 and 4 are vertical angles.
Vertical angles are congruent.
reciprocals
Two numbers that have a product of 1
2 3 and are reciprocals
3 22 3
= 13 2
15 and are reciprocals
51
5 = 15
13 and are reciprocals
31
3 = 13
Perpendicular lines
Two lines that intersect and form a right angle
A CE
B
D
AC BD
BEC is a
right angle.
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Prime notation
When figures are transformed, prime notation is often used to name the image.
The point P’ (read P prime) is the image of point P
B'
A'
C'
B
A
C
8
7
6
5
4
3
2
1
-1
-2
-3
-4
-5
-6
2 3 4 5 6 7 8-1-2-3-4-5-6-7-8 1
Reflect DABC across the x-axisDABC DA’B’C’
x
y
Tesselation
Repeating pattern of figures that fills a plane completely
No overlapping of figures, no gap between figures
Tangent to a circle
Line that intersects the circle in exactly one
pointIs perpendicular to the radius of the circle at the point of intersection, called point of tangency
B
A
D
AD is tangent to circle B
at point A.
AD AB point A.
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Quadratic formula
Used to find the solution to a quadratic equation in standard form
x2 + bx + c = 0
2 4 =
2
b b acx
a
Favorable event or outcome
In probability the outcome your are interested in measuring
Example: Rolling two dice and getting a one on each die.
Perpendicular bisector
Line, line segment, or ray that is perpendicular to a line segment at
its midpoint
BA C
D
E
Line DE is perpendicular to segment AC at midpoint B.
DE is the perpendicular bisector of segment AC.
Conditional statement
Statement in the form of If ___, then ___.
If an angle is a right angle, then its measure is 90o.
If a triangle is a right triangle, then it has a right angle.
secant of a circle
A line that intersects a circle in two points
B
AC AB is a secant of
circle C.
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