2.5.3 Journal: Proofs of Congruence

The Engineers' Conjectures: The engineers are designing a bridge truss, and they need to prove that two triangles inside the truss are congruent.
1. Complete the table to summarize what you know about each engineer's conjecture: (2 points: 1 point for each row of the chart)
Engineer Conjecture

Natalie


Emma


2. Analyze the conjectures. Who do you think is correct, and why? (1 point)






Analyzing the Data
3. Here is a picture of the bridge truss, and the given information:

Fill out the two-column proof to prove that BED BEF. You may not need to use all the rows. (5 points)
Statement Reason




4. State how you know that BDF is an isosceles triangle. (2 points)



5. Using the previous problem, fill out the two-column proof that ABD CBF. You may not need to use all t

Respuesta :

Statement Reason

AB and BC are congruent

CPCTC

DB and FB are congruent

CPCTC

Angle EBD congruent to angle EFB

CPCTC

Angle ABD congruent to angle EBD

Alternate angle theorem

Angle FBC congruent to angle EFB

Alternate angle theorem

ABD CBF

SAS theorem


Two angles, sides or figure are said to be congruent when they are equal

1. Question: The given parameters in the question are resented as follows;

[tex]\overline{AC} \parallel \overline{DF}[/tex]

The midpoint of the line [tex]\overline{DF}[/tex], is the point E

The midpoint of the line [tex]\overline{AC}[/tex], is the point B

The line [tex]\overline{EB} \perp \overline{AC}[/tex]

1. Required:

To complete the table from the question

Solution:

Engineer [tex]{}[/tex]                      Conjecture

Natalie

SAS             [tex]{}[/tex]                  ΔABD ≅ ΔCBF

Summary: Natalie's statement is that ΔABD is congruent to ΔCBF by Side Angle Side rule of congruency

Emma

SSS             [tex]{}[/tex]                  ΔABD ≅ ΔCBF

Summary: Emma's statement is that ΔABD is congruent to ΔCBF by Side Side Side rule of congruency

2. Required:

Analysis of the two conjectures

Solution:

Given that the information on ΔABD and ΔCBF are based on the relative lengths of the height and base of both triangles, and that both refer to the same triangle, both are correct. However, there are no direct information with regards to the sides [tex]\overline{AD}[/tex], and [tex]\overline{CF}[/tex], Therefore, Natalie's conjecture is based directly on the given information

3. Required:

To prove that  ΔBED ≅ ΔBEF

The two column proof is presented as follows;

Statement    [tex]{}[/tex]                                   Reason

1. E is the point [tex]\overline{DF}[/tex]     [tex]{}[/tex]              1. Given

2. [tex]\overline{DE}[/tex] = [tex]\overline{EF}[/tex]    [tex]{}[/tex]                            2. By definition of midpoint of  [tex]\overline{DF}[/tex]

3. [tex]\overline{EB} \perp \overline{AC}[/tex]     [tex]{}[/tex]                           3. Given

4. ∠BED = ∠BEF = 90°     [tex]{}[/tex]          4. By definition of [tex]\overline{EB} \perp \overline{AC}[/tex]

5. [tex]\overline{EB} \cong\overline{EB}[/tex]    [tex]{}[/tex]                           5. Reflexive property

6. ΔBED ≅ ΔBEF  [tex]{}[/tex]                      6. Side Angle Side, (SAS) rule of congruency

4. Required:

To state how ΔBDF is an isosceles triangle

Solution:

Triangle ΔBDF is an isosceles triangle because by Congruent Parts of Congruent Triangles are Congruent, CPCTC, [tex]\mathbf{\overline{BD}=\overline{BF}}[/tex], therefore, given that two sides of ΔBDF are equal, ΔBDF is an isosceles triangle by definition

5. Required:

To fill out the proof that ΔABD ≅ ΔCBF

Solution;

Statement    [tex]{}[/tex]                                Reason

1. B is the point [tex]\overline{AC}[/tex]     [tex]{}[/tex]               1. Given

2. [tex]\overline{BC}[/tex] = [tex]\overline{AB}[/tex]    [tex]{}[/tex]                            2. By definition of midpoint of  [tex]\overline{AC}[/tex]

3. [tex]\overline{BD}=\overline{BF}[/tex]    [tex]{}[/tex]                           3. ΔBED ≅ ΔBEF (or ΔBDF is an isosceles Δ)

4. ∠BDE = ∠BFE    [tex]{}[/tex]                    4. Base angles of isosceles ΔBDF

5. ∠ABD = ∠BDE, ∠CBF = ∠BFE     [tex]{}[/tex]   [tex]{}[/tex] 5. Alternate angle theorem

6.  ∠ABD = ∠CBF   [tex]{}[/tex]                    6. Transitive property

7. ΔABD ≅ ΔCBF  [tex]{}[/tex]                      7. Side Angle Side, (SAS) rule of congruency

Learn more about two column proofs here:

https://brainly.com/question/13969040

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