Download 3.1

Geometry {Mr. Yealu}
Name: __________________________
Mon., 11-07-11
3.1 – 3.4 quiz: Tues., 11-15-2011
only a hot-hot-hot piece of cake!! (trust me)
[3.1 – What Are Congruent Figures?]
Conceptualization: Every triangle has six parts -- three angles and three sides.
 A  F, B  E, and C  D

When we say that ABC  FED, we mean that: and

AB  FE, BC  ED, and CA  DF.
Remember (from Chapter 1), an arrow symbol {  } means "implies" {"If ...., then ...."}.
If the arrow is doubled {  }, the statement is reversible. {That is, both the statement
and the converse are true.} This is called a biconditional.
Definition: Congruent triangles  all pairs of corresponding parts are congruent
Congruent polygons  all pairs of corresponding parts are congruent
Whenever a side or an angle is shared by two figures, we can say that the side or angle is
congruent to itself. This property is called the Reflexive Property.
In 1 – 2, justify each conclusion with one of the properties you learned in Chapter 2 and in 3.1:
M
Given: M and N are mdpts;
1.
D
DC  AB; AB  DB;
1 
4; 2 
4
Conclusions
ADC 
Reasons
ABC
C
1
3
A
1.
2
1.
2. CM  AN
2.
3. BD  DB
3.
4. DC  DB
4.
N
3
B
3.2 – Three Ways To Prove Triangles Congruent]
Postulate: If there exists a correspondence between the vertices of two triangles such
that three sides of one triangle are congruent to the corresponding sides of
the other triangle, the two triangles are congruent. {SSS}
Postulate: If there exists a correspondence between the vertices of two triangles such
that two sides and the included angle of one triangle are congruent to the
corresponding parts of the other triangle, the two triangles are congruent.
{SAS}
Postulate: If there exists a correspondence between the vertices of two triangles such
that two angles and the included side of one triangle are congruent to the
corresponding parts of the other triangle, the two triangles are congruent.
{ASA}
3.1 homework: p. 114 #’s 1 – 3
3.1 – 3.3 quiz: Tues., 11-15-2011