Congruent Triangles in Geometry

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Questions and Answers

Which postulate can be used to prove two triangles are congruent if all three sides of one triangle are congruent to the corresponding three sides of another triangle?

  • ASA Postulate
  • SAS Postulate
  • SSS Postulate (correct)
  • AAS Postulate

If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, which postulate proves the two triangles are congruent?

  • AAS Postulate
  • SSS Postulate
  • SAS Postulate (correct)
  • ASA Postulate

Two angles and the included side of one triangle are congruent to two angles and the included side of another triangle. Which postulate proves congruence?

  • SAS Postulate
  • ASA Postulate (correct)
  • SSS Postulate
  • AAS Postulate

Two angles and a non-included side of one triangle are congruent to two angles and a non-included side of another triangle. What postulate proves congruence in this case?

<p>AAS Postulate (D)</p> Signup and view all the answers

What is the name for a triangle that can be divided into multiple smaller triangles?

<p>Composite Triangle (B)</p> Signup and view all the answers

What property states that any segment or angle is congruent to itself?

<p>Reflexive Property (C)</p> Signup and view all the answers

If point M is the midpoint of segment AB, what can be concluded about segments AM and MB?

<p>AM is congruent to MB (B)</p> Signup and view all the answers

In a proof, it is stated that segment BD is congruent to segment BD. Which property justifies this statement?

<p>Reflexive Property (C)</p> Signup and view all the answers

Which postulate proves two triangles congruent if two angles and the included side of one triangle are congruent to the corresponding parts of another triangle?

<p>ASA Postulate (D)</p> Signup and view all the answers

If $\overline{AB} \cong \overline{XY}$ and $\overline{BC} \cong \overline{YZ}$, what additional congruence is needed to prove $\triangle ABC \cong \triangle XYZ$ by SAS?

<p>$\angle B \cong \angle Y$ (B)</p> Signup and view all the answers

What property justifies the statement that $\overline{PQ} \cong \overline{PQ}$?

<p>Reflexive Property (A)</p> Signup and view all the answers

If $\angle ABC \cong \angle DEF$ and $\angle BCA \cong \angle EFD$, what additional congruence is needed to prove $\triangle ABC \cong \triangle DEF$ by AAS?

<p>$\overline{AB} \cong \overline{DE}$ (D)</p> Signup and view all the answers

Which of the following statements is true regarding an angle bisector?

<p>An angle bisector creates two congruent angles. (D)</p> Signup and view all the answers

If point M is the midpoint of segment $\overline{AB}$, what conclusion can be drawn?

<p>$\overline{AM} \cong \overline{MB}$ (B)</p> Signup and view all the answers

What does CPCTC stand for?

<p>Corresponding Parts of Congruent Triangles are Congruent (C)</p> Signup and view all the answers

In $\triangle ABC$ and $\triangle DEF$, if $\overline{AB} \cong \overline{DE}$, $\overline{BC} \cong \overline{EF}$, and $\overline{AC} \cong \overline{DF}$, what postulate proves $\triangle ABC \cong \triangle DEF$?

<p>SSS Postulate (D)</p> Signup and view all the answers

Which term describes the intersection of two lines forming two pairs of congruent opposite angles?

<p>Vertical Angles (B)</p> Signup and view all the answers

If a segment is divided into three congruent segments, it is said that the segment is:

<p>Trisected (A)</p> Signup and view all the answers

Flashcards

SSS Postulate

If three sides of one triangle are congruent to the three sides of another triangle, then the triangles are congruent.

SAS 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 triangles are congruent.

ASA 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 triangles are congruent.

AAS Postulate

If two angles and a non-included side of one triangle are congruent to two angles and a non-included side of another triangle, then the triangles are congruent.

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Composite Triangle

A triangle that can be divided into two smaller triangles.

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Vertical Angles

When two lines intersect, they form two pairs of vertical angles, which are always congruent.

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Reflexive Property

Any segment or angle is congruent to itself.

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Midpoint

A midpoint divides a segment into two congruent segments.

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Angle Bisector

A ray that divides an angle into two congruent angles.

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SAS Postulate (Side-Angle-Side)

If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent.

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AAS Postulate (Angle-Angle-Side)

If two angles and a non-included side of one triangle are congruent to two angles and the corresponding non-included side of another triangle, then the triangles are congruent.

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ASA Postulate (Angle-Side-Angle)

If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent.

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SSS Postulate (Side-Side-Side)

If three sides of one triangle are congruent to three sides of another triangle, then the triangles are congruent.

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CPCTC (Corresponding Parts of Congruent Triangles are Congruent)

If two triangles are congruent, then their corresponding sides and angles are congruent.

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Segment Trisector

A line segment that divides another line segment into three congruent segments.

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Definition of Congruent Segments

If two segments are equal in length, then they are congruent.

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Study Notes

Determining Congruent Triangles

  • SSS Postulate (Side-Side-Side): If three sides of one triangle are congruent to the three sides of another triangle, then the triangles are congruent.
  • SAS Postulate (Side-Angle-Side): If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent.
  • ASA Postulate (Angle-Side-Angle): If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent.
  • AAS Postulate (Angle-Angle-Side): If two angles and a non-included side of one triangle are congruent to two angles and a non-included side of another triangle, then the triangles are congruent.

Common Triangle Proofs

  • Composite Triangle: A triangle that can be divided into two smaller triangles.
  • Vertical Angles: When two lines intersect, they form two pairs of vertical angles, which are always congruent.
  • Reflexive Property: Any segment or angle is congruent to itself.
  • Midpoint: A midpoint divides a segment into two congruent segments.

Example Proofs

  • Example 1: Prove triangle ABD is congruent to triangle CBD using the given information that AD is congruent to CD and B is the midpoint of AC.

    • Statement: AD is congruent to CD
      • Reason: Given
    • Statement: B is the midpoint of AC
      • Reason: Given
    • Statement: AB is congruent to BC
      • Reason: Definition of Midpoint
    • Statement: BD is congruent to BD
      • Reason: Reflexive Property
    • Statement: Triangle ABD is congruent to triangle CBD
      • Reason: SSS Postulate (Statements 1, 3, and 4)
  • Example 2: Prove triangle MRO is congruent to triangle PRO using the given information that segment RO is perpendicular to segment MP and segment MO is congruent to segment OP.

    • Statement: MO is congruent to OP
      • Reason: Given
    • Statement: RO is perpendicular to MP
      • Reason: Given
    • Statement: Angle MOR is congruent to angle POR
      • Reason: Perpendicular lines form right angles.
    • Statement: RO is congruent to RO
      • Reason: Reflexive Property
    • Statement: Triangle MRO is congruent to triangle PRO
      • Reason: SAS Postulate (Statements 1, 3, and 4)
  • Example 3: Prove triangle ABC is congruent to triangle ECD using the given information that angle one is congruent to angle 4 and segment AC is congruent to segment EC.

    • Statement: Angle 1 is congruent to angle 4
      • Reason: Given
    • Statement: Segment AC is congruent to segment EC
      • Reason: Given
    • Statement: Angle 2 is congruent to angle 3
      • Reason: Vertical angles are congruent.
    • Statement: Triangle ABC is congruent to triangle ECD
      • Reason: ASA Postulate (Statements 1, 2, and 3)
  • Example 4: Prove triangle ABE is congruent to triangle DCE using the given information that segment AB is congruent to segment CD, segment AE is congruent to segment DE, and angle 1 is congruent to angle 4.

    • Statement: Segment AB is congruent to segment CD
      • Reason: Given
    • Statement: Segment AE is congruent to segment DE
      • Reason: Given
    • Statement: Angle 1 is congruent to angle 4
      • Reason: Given
    • Statement: Angle 2 is congruent to angle 3
      • Reason: If two angles are congruent, then their supplementary angles are congruent.
    • Statement: Triangle ABE is congruent to triangle DCE
      • Reason: AAS Postulate (Statements 1, 3, and 4)

Proving Triangles Congruent

  • SAS Postulate (Side-Angle-Side): If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, the triangles are congruent.
  • AAS Postulate (Angle-Angle-Side): If two angles and a non-included side of one triangle are congruent to two angles and the corresponding non-included side of another triangle, the triangles are congruent.
  • SSS Postulate (Side-Side-Side): If three sides of one triangle are congruent to three sides of another triangle, the triangles are congruent.
  • ASA Postulate (Angle-Side-Angle): If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, the triangles are congruent.

Proving Triangles Congruent through Midpoints and Angle Bisectors

  • Midpoint: A midpoint divides a segment into two congruent segments.
  • Angle Bisector: An angle bisector is a ray that divides an angle into two congruent angles.
  • Vertical Angles: Vertical angles are congruent.

Proving Triangles Congruent Through Trisectors

  • Segment Trisector: A segment trisector divides a segment into three congruent segments.

Proving Triangles Congruent By Combining Strategies

  • Segment Addition Property: To prove two segments are congruent, add a common segment to both sides of an equation that states two other segments are congruent.
  • Definition of Congruent Segments: Segments are congruent if they have equal lengths.
  • Definition of Congruent Angles: Angles are congruent if they have the same measure.

CPCTC (Corresponding Parts of Congruent Triangles are Congruent)

  • If two triangles are congruent, then their corresponding sides and angles are congruent.

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