It is known that: as shown in the figure, in △ ABC, AC = BC, ∠ ACB = 120 °, CE is perpendicular to AB and D, and de = DC

It is known that: as shown in the figure, in △ ABC, AC = BC, ∠ ACB = 120 °, CE is perpendicular to AB and D, and de = DC

∵ AC = BC, ∠ ACB = 120 °, ∵ a = ∠ ABC = 30 °, ∵ CE ⊥ AB, CD = De, ∵ AB vertical bisection CE, ∵ BC = be, ∵ Ba bisection ∠ CBE, ∵ CBE = 2 ∠ CBA = 60 ° and ∵ BCE