Name:_________________________________
Math Essentials
Activity 6 Definitions, Postulates, Properties & Theorems
Term
“Definition”
Example
(OR postulate, property, theorem)
* right angle
an angle that measures exactly 90
* straight angle
an angle that measures exactly
180
* complementary
angles
two angles whose measures have the sum of
* supplementary
angles
two angles whose measures have the sum of
* linear pair
two adjacent angles that are supplementary
CONGRUENT
geometric figures with equal measures
* congruent
angles
angles that have the same measure
90
180
*see congruent angles & congruent
segments
D  E
*congruent segments
segments that have the same measure
* vertical angles
angles opposite one another at the intersection
of two lines; they are congruent
Given: AB  CD , we can
Conclude: AB  CD.
1& 3, 2&4
*Vertical Angles
Theorem
Vertical angles are congruent.
1  3 and 2  4
Term
“Definition”
Example
(OR postulate, property, theorem)
*Segment Addition
Postulate
Given that Q is a point between endpoints P
*Angle Addition
Postulate
If P is in the interior of RST , then
mRSP  mPST  mRST .
and R of PR , PQ  QR  PR .
mRSP  mPST  mRST
*midpoint of a Segment
the point on the segment that divides it into
two congruent segments
M is the ____ of AB
*bisect
When you ______ a geometric figure, you
divide it into two equal or congruent parts.
BD bisects ABC
*angle bisector
BG bisects AC at point B.
A ray that divides an angle into two congruent
adjacent angles.
If BD _____ ABC , then
ABD  DBC
*perpendicular lines*
Lines that intersect to form a right angle.
AB  CD