BC first because: AB=AC.

So: angle ABC= angle ACB, and because: angle B= angle C.

So: angle CBD= angle BCD

In triangle DBC, because: Angle CBD= Angle BCD, DB=DC (equilateral and equilateral) triangle theorem.

Two questions:

In a right triangle, because

AC=6，BC=8

So: AB= 10 (Pythagorean theorem)

Because point C coincides with point E, DC = Germany.

So the triangle ACD is equal to the triangle AED(DC = DE? Angle C= angle E=90 degrees? AD=AD)

So what? AC=AE=6

So what? BE= 10-AE=4

Triangular bed is similar to triangular BCA.

So BE/BC=BD/BA=DE/AC.

So BD=5

So CD=3