Angle Bisector of the Vertex Angle

What does ray AD do to vertex angle BAC? Measure angle ADC. What kind of triangles are ABD and ACD? Draw triangle ABD on top of what you see. Is it congruent to triangle ACD? Verify by trying to find a transformation that maps ABD onto ACD. Complete this conditional statement based on what you observed in this diagram. If the vertex angle of an isosceles triangle is ______________________________, then ___________________________________________________________________________________ .