Download 4-6 Congruence in Right Triangles

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Transcript
Review: Solving Systems
x+y
x
2y+3
12
Find the values of x and y that make the following triangles
congruent.
Congruent Triangles (CPCTC)
Two triangles are congruent triangles if and
only if the corresponding parts of those
congruent triangles are congruent.
• Corresponding
sides are
congruent
• Corresponding
angles are
congruent
Congruence Statement
When naming two congruent triangles, order
is very important.
Third Angle Theorem
If two angles of one triangle are congruent to
two angles of another triangle, then the
third angles are also congruent.
Congruence Shortcuts
Side-Angle-Side (SAS) Congruence Postulate:
If two sides and the included angle of one triangle
are congruent to two sides and the included
angle of another triangle, then the two triangles
are congruent.
Side-Side-Side Congruence Postulate
SSS Congruence Postulate:
If the three sides of one triangle are congruent to
the three sides of another triangle, then the two
triangles are congruent.
Congruence Shortcuts
Angle-Side-Angle (ASA) Congruence Postulate:
If two angles and the included side of one triangle
are congruent to two angles and the included
side of another triangle, then the two triangles
are congruent.
Congruence Shortcuts
Angle-Angle-Side (AAS) Congruence Theorem:
If two angles and a non-included side of one
triangle are congruent to the corresponding two
angles and the non-included side of another
triangle, then the two triangles are congruent.
Base Angles Theorem:
If two sides of a triangle
are congruent, then
the angles opposite
them are congruent.
Converse of the Base Angles Theorem:
If two angles of a
triangle are
congruent, then the
sides opposite them
are congruent.
Equilateral Triangle Theorem
A triangle is equilateral if and only if it is
equiangular.

Practice
Practice
Practice
Congruence in Right
Triangles
Vocabulary Right Triangles
A
Hypotenuse
Leg
B
Leg
C
Hypotenuse-Leg Theorem
Hypotenuse-Leg (HL) Congruence Theorem:
If the hypotenuse and a leg of a right triangle are
congruent to the hypotenuse and leg of another
right triangle, then the two triangles are
congruent.
• To use the HL Theorem, you must show that three conditions
are met:
• There are two right triangles
• The triangles have congruent hypotenuses
• There is one pair of congruent legs
Using the HL Theorem
Using the HL Theorem
Statements
1. AD is the  bisector of CE ,
Reasons
1.
CD  EA
2.
2. Defn. of 
3. CBD & EBA are rt. s
3.
4. CB  EB
4.
5.
5. HL Thm.
Using the HL Theorem
Statements
Reasons
1. PRS and RPQ are rt s
SP  QR
1.
2.
2. Defn. of rt s
3.
3. Refl. Prop. of 
4. PRS  RPQ
4.
Which are congruent by HL?
E
A
F
J
3in
B
5in
C
3in
5in
H
3in
D
5in
G
Which are congruent by HL?
E
A
F
J
3in
B
5in
C
3in
5in
H
3in
D
5in
G
HFJ 
DEG
Prove the triangles are congruent
P
S
Q
R
1. QPR and SRP
are right, SP  RQ
Given
2. QPR  SRP
All Right angles are
congruent
3. PR  PR
Reflexive
4.
SRP 
QPR
HL Theorem
What else do you need to prove the triangles
are congruent?
R
Is RT  XT?
or
Is XV  TV?
X
V
T
Prove the two triangles are congruent
R
1. T is the midpoint
of RV
S and U are
right angles
RS  TU
3.
RST 
TUV
T
S
1. Given
U
2. Definition of midpoint
2. RT  TV
T is the midpoint
of RV
3. HL Theorem
V