Please, please.

On d, DQ is perpendicular to AE, q is perpendicular to DN, AB is perpendicular to n, and DQ=DN because AD is the bisector.

Because angle ECD+ angle ACD= 180, and because angle ACD+ angle ABD= 180.

So angle ABD= angle ECD.

In triangle DQC and triangle DNB

Angle ABD= Angle ECD, Angle DQC= Angle DNB = 90, DQ=DN.

So the triangle DQC congruent triangles DNB(AAS)

So CD = db