We are given ab // de. because the lines are parallel and
segment cb crosses both lines, we can consider segment
cb a transversal of the parallel lines. angles ced and cba
are corresponding angles of transversal cb and are
therefore congruent, so zced 2 zcba. we can state zc
~ 2c using the reflexive property. therefore, acb -
adce by the
aa similarity theorem.
sss similarity theorem.
aas similarity theorem.
asa similarity theorem.