1 1, proving that ∫△Abd, △AEC are equilateral triangles, ∴AD=AB, AC=AE.

∠ DAB = ∠ EAC = 60, ∴∠DAB+∠BAC=∠EAC+∠BAC, that is ∠DAC=∠BAE,

In △ADC and △ABE, AD = AB, ∠DAC=∠BAE, AC=AE, ∴△ADC≌△ABE(SAS).

∴DC=BE

13, ∫OE bisects ∠AOB, ED⊥OB, EC⊥OA, and the vertical feet are d and C ∴ ED = EC respectively.

∴∠ ED=EC =∠ ECD, in Rt△ODE and Rt△OCE, OE = OE, ED = EC,

∴Rt△ODE≌Rt△OCE(HL), ∴ od = oc, ∴△ODC are isosceles triangles,

And ∵OE is the bisector of ∠DOC, and ∴OE is the height and center line on the bottom CD, that is, OE is the vertical plane of the line segment DC.

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