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Transcript
Given: 𝐡𝐺 βŠ₯ 𝐹𝐻, 𝐹𝐺 β‰… 𝐺𝐻
Prove βˆ†πΉπ΅πΊ β‰… βˆ†π»πΊπ΅
B
Statements
Reasons
1. 𝐡𝐺 βŠ₯ 𝐹𝐻, 𝐹𝐺 β‰… 𝐺𝐻
1. Given
2. ∠𝐡𝐺𝐹 π‘Žπ‘›π‘‘ ∠𝐡𝐺𝐻 =
90°
2. Definition of βŠ₯
3. ∠𝐡𝐺𝐹 β‰… ∠𝐡𝐺𝐻
3. Right Angle
Congruence Theorem
4. 𝐡𝐺 β‰… 𝐡𝐺
4. Reflexive Property
5. βˆ†πΉπ΅πΊ β‰… βˆ†π»πΊπ΅
5. SAS
F
G
H
Chapter 4.5: Triangle Congruence
Continues
You will learn two more ways to
prove two triangles are congruent
Activity 1: ASA.
β€’ Below is a partially drawn triangle. In this
case, AB has been drawn and two angles have
been created. If you extend two sides from ∠a
and ∠b, how many different triangles can you
create?
A
B
Postulate 21: Angle-Side-Angle (ASA)
Congruence
β€’ If two Angles and the
included Side of one
triangle are congruent
to two Angles and an
included Side of
another triangle, then
the two triangles are
congruent.
Using ASA in a Proof
P
Q
S
R
Given: 𝑃𝑄 βˆ₯ 𝑆𝑅, 𝑃𝑆 βˆ₯ 𝑄𝑅
Prove: βˆ†π‘ƒπ‘„π‘† β‰… βˆ†π‘…π‘†π‘„
Statements
Reasons
1. 𝑃𝑄 βˆ₯ 𝑆𝑅, 𝑃𝑆 βˆ₯ 𝑄𝑅
1. Given
2. βˆ π‘ƒπ‘„π‘† β‰… βˆ π‘…π‘†π‘„
2. Alternate Interior Angles
3. βˆ π‘ƒπ‘†π‘„ β‰… βˆ π‘…π‘„π‘†
3. Alternate Interior Angles
4. 𝑄𝑆 β‰… 𝑆𝑄
4. Reflexive Property
5. βˆ†π‘ƒπ‘„π‘† β‰… βˆ†π‘…π‘†π‘„
5. ASA
Flow Chart Proofs
P
Q
S
R
Given: 𝑃𝑄 βˆ₯ 𝑆𝑅, 𝑃𝑆 βˆ₯ 𝑄𝑅
Prove: βˆ†π‘ƒπ‘„π‘† β‰… βˆ†π‘…π‘†π‘„
Flow Chart Proofs
Q
P
Given: 𝑃𝑄 βˆ₯ 𝑆𝑅, 𝑃𝑆 βˆ₯ 𝑄𝑅
Prove: βˆ†π‘ƒπ‘„π‘† β‰… βˆ†π‘…π‘†π‘„
𝑃𝑄 βˆ₯ 𝑆𝑅
Given
𝑃𝑆 βˆ₯ 𝑄𝑅
Given
S
R
βˆ π‘ƒπ‘„π‘† β‰… βˆ π‘…π‘†π‘„
Alternate Interior Angles
βˆ π‘ƒπ‘†π‘„ β‰… βˆ π‘…π‘„π‘†
Alternate Interior Angles
𝑄𝑆 β‰… 𝑆𝑄
Reflexive Property
βˆ†π‘ƒπ‘„π‘† β‰… βˆ†π‘…π‘†π‘„
ASA
Postulate 21: Angle-Angle-Side (AAS)
Congruence
β€’ If two Angles and a nonincluded Side of one
triangle are congruent
to two Angles and the
corresponding nonincluded Side of
another triangle, then
the two triangles are
congruent.
Using ASA to prove AAS
Given: βˆ π’‚ β‰… βˆ π’™, βˆ π’„ β‰… βˆ π’›, 𝑨𝑩 β‰… 𝑿𝒀
Prove: βˆ†π‘¨π‘©π‘ͺ β‰… βˆ†π‘Ώπ’€π’
ASA
Using ASA to prove AAS
Given: βˆ π’‚ β‰… βˆ π’™, βˆ π’„ β‰… βˆ π’›, 𝑨𝑩 β‰… 𝑿𝒀
Prove: βˆ†π‘¨π‘©π‘ͺ β‰… βˆ†π‘Ώπ’€π’
βˆ π’‚ β‰… βˆ π’™
Given
βˆ π’ƒ β‰… βˆ π’š
Third Angle Theorem
βˆ π’„ β‰… βˆ π’›
Given
𝑨𝑩 β‰… 𝑿𝒀
Given
βˆ†π‘¨π‘©π‘ͺ β‰… βˆ†π‘Ώπ’€π’
ASA
Triangle Congruence Theorems and
Postulates
Theorems and Postulates the
Prove Triangle Congruence:
β€’
β€’
β€’
β€’
β€’
Side-Side-Side (SSS)
Side-Angle-Side (SAS)
Hypotenuse-Leg (HL)
Angle-Side-Angle (ASA)
Angle-Angle-Side (AAS)
These do not prove congruence:
Do not Use
β€’ Angle-Angle-Angle
(AAA)
β€’ The Donkey Conjecture:
(SSA)