6. Andre is thinking through a proof using a reflection to show that a triangle is isosceles given that its base angles are congruent. Complete the missing information for his proof. B Construct AB such that AB is the perpendicular bisector of segment CD. We know angle ADB is 1 2 DB is congruent to congruent to Angle 3 is congruent to angle angles. Triangle ABC is congruent to triangle Congruence Theorem. AD is congruent to since AB is the perpendicular bisector of CD. because they are both right 4 5 because of the 6 Triangle 7 because they are corresponding parts of congruent triangles. Therefore, triangle ADC is an isosceles triangle.