A
proof – is a logical argument
that shows a statement is true.
For every statement that is made,
you have a valid reason to back it
up.
 A postulate – is a rule that is
accepted without proof.
 A theorem – is a statement that
can be proven.
If B is between A and C, then
AB + BC = AC.
or
If AB + BC = AC, then B is
between A and C.
A
B
C
If P is in the interior of angle RST, then
the measure of angle RST is equal to
the sum of the measures of angle RSP
and angle PST…or…
mRSP  mPST  mRST
P
R
T
S

Reflexive: For any segment AB,

Symmetric: If AB  CD , then CD  AB

AB  AB .
Transitive: If AB  CD and CD  EF ,
then AB  EF .

Reflexive: For any angle A, A  A .

Symmetric: IfA  B , then B  A .

Transitive: If A  B and B  C ,
thenA  C .