As shown in the figure, in the semicircle AOB, ad = DC, ∠ cab = 30 °, AC = 23, the length of ad is calculated

As shown in the figure, in the semicircle AOB, ad = DC, ∠ cab = 30 °, AC = 23, the length of ad is calculated

∵ AB is the diameter, ∵ ACB = 90 °, ∵ cab = 30 °, ∵ ABC = 60 °, ∵ arc BC degree = 12 arc AC degree; ∵ ad = DC, ∵ arc ad degree = arc DC degree = 12 arc AC degree, ∵ arc BC degree = arc ad degree; ∵ BC = ad