The isosceles triangle having an angle bisector [tex]\overline{AD}[/tex] forms two congruent triangles.
Reasons:
The given parameters are;
ΔABC is an isosceles triangle.
[tex]\overline{AB}[/tex] ≅ [tex]\overline{AC}[/tex]
[tex]\overline{AD}[/tex] bisects ∠BAC
Therefore, the proof that ∠ABD ≅ ∠ACD is given as follows;
1. [tex]\overline{AB}[/tex] ≅ [tex]\mathbf{\overline{AC}}[/tex] (Given)
2. [tex]\overline{AD}[/tex] bisects ∠BAC (Given)
3. ∠BAD ≅ ∠CAD (Definition of angle bisector)
4. [tex]\overline{AD}[/tex] ≅ [tex]\mathbf{\overline{AD}}[/tex] (Reflexive property of congruency)
5. ΔBAD ≅ ΔCAD (Side Angle Side, SAS rule of congruency based on steps 1, 3 and 4)
6. ∠ABD ≅ ∠ACD (Congruent Parts of Congruent Triangle are Congruent, CPCTC)
Learn more about SAS rule of congruency here:
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