Given: Points C,E,B and A,E,D are collinear

Prove: AE / CE = AB / CD

AE / CE = AB / CD
triangle AEB ~ triangle CED
<DAB =<DCB
<AEB = <CED
Inscribed angle measures half its intercepted arc
<DAB=(1/2) * (arc DB) and <DCB=(1/2) * (arc DB)
Definition
Substitution
AA similarity
Vertical angles are equal