Solution: Because S △ Abe = bexadx1/2s △ AEC = ecxadx1/2, and AE is the center line of △ABC, the area of BE=EC is equal.

The center line of a regular triangle divides the triangle into two small triangles with equal areas.

2. △ADC perimeter =AD+DC+AC

△ Abdominal circumference =AD+BD+AB

And BD=DC because AD is the center line on the side of BC.

The circumference of △ADC is 3cm more than that of △ABD.

Therefore, △ADC perimeter -△ABD perimeter =

So AC-AB=3, AC+AB= 13, so AC=8 cmAB=5cm.

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