Because we know from ② ③ ④ that this is a regular triangle, from ① that CD is the height of the side, and from ② that Be is the height of the side, we get that ⑤ holds.

The second question, ② ③ ④

The third question is known: BE⊥AC, AE=CE, ∠ Abe = 30?

Verification: CD=BE

Proof: Because BE⊥AC, AE=CE, this is an isosceles triangle, because ∠ Abe = 30? So this is a regular triangle. Because AC=BC, CD is on the same side, and angle A= angle CBD, so triangle ACD and BCD are congruent (SSA), so AD=BD, so CD⊥AB and three lines are integrated. So CD=BE