C. D is the point outside the line AB, and Ca = CB, Da = ab Please use the theorem of vertical bisector. No auxiliary line is allowed

Because CA = CB, so C is on the vertical bisector of AB, your question should be Da = dB. Similarly, D is on the vertical bisector of AB, so. CD is on the vertical bisector of ab

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1. As shown in the figure, D is a point in the quadrilateral aebc, connecting AD and BD. it is known that Ca = CB, Da = dB and EA = EB. (1) are the three points c, D and E in a straight line? Why? (2) If AB = 24, ad = 13, CA = 20, what is the length of CD?
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