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The first day mathematics moving point finale problem. (A complete process is required)
When the angle BDA= 1 10 degrees, the triangle ADE is an isosceles triangle.

Proof: Because the angle BDA== 1 10, the angle B=40 degrees.

So the angle BAD=30 degrees

Because AB=AC and angle B=40 degrees.

So the angle BAC= 100 degrees.

So the angle DAE=70 degrees

In the triangle ADE, because the angle DAE=70 degrees, the angle ADE=40 degrees.

AED angle =70 degrees.

So AD=ED

So triangle ADE is an isosceles triangle.