Question 1099765
AB is congruent with EB because B is the midpoint of AE
BC is congruent with BD because B is the midpoint of CD
Point B, belonging to lines AE and CD is the intersection of those lines
Two pairs of vertical angles are formed by the intersection of those lines.
Angles ABD and EBC are one of those vertical pairs.
Because they are a pair of vertical angles, angles ABD and EBC are congruent.
Triangles ABD and EBC are congruent by side-angle-side congruency,
because they have
AB congruent with EB,
BD congruent with BC,
and between those pairs of congruent sides they have
angle ABD congruent with angle EBC.
Because Corresponding Parts of Congruent Triangles are Congruent (CPCTC),
angle ADB is congruent with angle ECB.