4.8
Step 2: ADK and RDK are congruent.
Step 3: D is the midpoint of AR. KD is an angle bisector
Step 4: ADK and RDK have equal measurements since KD bisects the angle which makes them congruent to each other. They are supplementary.
conjecture:In an isosceles triangle, the bisector of the vertex angle is also the altitude and the median to the base