## Elementary Geometry for College Students (5th Edition)

$\overline{AC}$ $\cong$ $\overline{BD}$
In part (a) we determined that the three segments, $\overline{AB}$, $\overline{BC}$, and $\overline{CD}$, are all congruent to each other. Therefore, $\overline{AB}$ $\cong$ $\overline{BC}$ $\cong$ $\overline{CD}$. Using the Segment Addition Postulate (twice), $\overline{AB}$ + $\overline{BC}$ $\cong$ $\overline{CD}$, and $\overline{BC}$ + $\overline{CD}$ $\cong$ $\overline{BD}$. If $\overline{AB}$ + $\overline{BC}$ $\cong$ $\overline{BC}$ + $\overline{CD}$, then $\overline{AC}$ $\cong$ $\overline{BD}$.