In parallelogram ABCD, E is the midpoint of AB and F is the midpoint of DC . Let G be the intersection of the diagonal DB and the line segment EF . Prove that G is the midpoint of EF.

Respuesta :

Answer:

GF = GE that prove G is the mid-point of EF

Step-by-step explanation:

In the Parallelogram ABCD

∵E is the mid-point of AB

∵F is the mid-point of CD

∵AB = CD opposite sides in the parallelogram

∴EB = DF⇒(1)

∵AB // CD opposite sides in the parallelogram

∴m∠EBD = m∠FDB alternate angles ⇒(2)

∵BD intersects EF at G

∴m∠BGE = m∠DGF vertically opposite angles ⇒(3)

By using (1) , (2) and (3) you can prove:

ΔBGE is congruent to ΔDGF ⇒ AAS

∴GF = GE

∴G is the mid-point of EF

The midpoint of the line [tex]\overline{EF}[/tex] is the point that divides [tex]\overline{EF}[/tex] in two halves of the same length.

  • ΔDFG ≅ ΔBGE and [tex]\overline{FG}[/tex] ≅ [tex]\overline{EG}[/tex] by CPCTC, therefore, G is the midpoint of [tex]\overline{EF}[/tex]

Reasons:

The given parameters are;

The midpoint of AB in parallelogram ABCD = E

The midpoint of DC = F

Point of intersection of EF and DB = Point G

Required:

To prove that point G is the midpoint of EF.

Solution:

Statement         [tex]{}[/tex]                       Reason

1. m∠BDC ≅ m∠ABD          [tex]{}[/tex]  1. Alternate angles theorem

2. m∠DGF ≅ m∠BGE           [tex]{}[/tex]2.Vertical angles theorem

3. [tex]\overline{DC}[/tex] = [tex]\overline {AB}[/tex]          [tex]{}[/tex]                  3. Opposite sides of a parallelogram ABCD

4. [tex]\overline{CF}[/tex] ≅ [tex]\overline{DF}[/tex]          [tex]{}[/tex]                 4. Definition of midpoint of DC

5. [tex]\overline{CF}[/tex] = [tex]\mathbf{\overline{DF}}[/tex]          [tex]{}[/tex]                  5. Definition of congruency

6. [tex]\overline{CF}[/tex] + [tex]\overline{DF}[/tex] = DC         [tex]{}[/tex]         6. Segment addition property

7. [tex]\overline{CF}[/tex] + [tex]\overline{CF}[/tex] = DC         [tex]{}[/tex]          7. Substitution property

8. 2·[tex]\overline{CF}[/tex] = DC        [tex]{}[/tex]                 8. Addition

9. [tex]\overline{CF}[/tex] = 0.5· [tex]\overline{DC}[/tex] = [tex]\overline{DF}[/tex]        [tex]{}[/tex]  9. Division property    

Similarly;

10. [tex]\overline{AE}[/tex] = 0.5·[tex]\overline{AB}[/tex] = [tex]\overline{EB}[/tex]         [tex]{}[/tex]  10. Division property

11. 0.5· [tex]\overline{DC}[/tex] = 0.5·[tex]\overline{AB}[/tex]         [tex]{}[/tex]     11. Multiplication property of equality

12. [tex]\overline{AE}[/tex] = [tex]\overline{EB}[/tex]          [tex]{}[/tex]                 12. Substitution property

13. ΔDFG ≅ ΔBGE     [tex]{}[/tex]             13. Angle-Angle-Side rule of congruency

14. [tex]\overline{FG}[/tex] ≅ [tex]\overline{EG}[/tex]                 [tex]{}[/tex]          14. CPCTC   [tex]{}[/tex]  

15. [tex]\overline{FG}[/tex] = [tex]\overline{EG}[/tex]     [tex]{}[/tex]                       15. Definition of congruency

16. Point G is the midpoint of [tex]\overline{EF}[/tex] [tex]{}[/tex]  17. Definition of midpoint

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