Answer:
A. ASA criterion for congruent triangles.
Step-by-step explanation:
Given DG is perpendicular bisector of CA and DH is perpendicular bisector of AB.
In triangle DGC and DGA
DG=DG( reflexive property of equality)
[tex]\angle DGA=\angle DGC=90^{\circ}[/tex] ( given )
[tex]\angle ADG=\angle CDG[/tex] ( by definition of perpendicular bisector)
[tex]\therefore \triangle AGD\cong \triangle CGD[/tex] ( ASA postulate)
Similarly, In triangle ADH and triangle BDH
DH=DH ( reflexive property of equality)
[tex]\angle DHA=\angle DHB=90^{\circ}[/tex] (given)
[tex]\angle ADH=\angle BDH[/tex] ( By definition of perpendicular bisector)
[tex]\therefore \triangle ADH\cong \triangle BDH[/tex] ( ASA postulate)
1.Statement: [tex]\overline{DG}\perp \overline{AC}[/tex]
Reason: Given.
2. Statemnet: AG=GC
Reason: Given
3. Statement: [tex]\overline{DG}[/tex] is perpendicular bisector of [tex]\overline{AC}[/tex]
Reason: from step 1 and step 2.
4.Statement: DA=DC
Reason: ASA criterion for congruent triangles.
5 .Statement:[tex]\overline{DH} \perp \overline{AB}[/tex]
Reason: Given
6. Statement:AH=HB
Reason:Given
7.Statement: [tex]\overline{DH}[/tex] si perpendicular bisector [tex]\overline{AB}[/tex]
Reason: By definition of perpendicular bisector.
8.Statement: DA=DB
Reason : ASA criterion for congruent triangles.
9.Statement: DC=DB
Reason: Transitive property of equality.
Hence proved.