Because point E is a point on the bisector of angle AOB, EC is perpendicular to OA and ED is perpendicular to OB.

So EC=ED (the distance from the point on the bisector of the angle is equal to both sides of the angle)

Because in the CDE triangle, EC=ED.

So angle ECD= angle EDC

2. Solution:

Because EC is vertical OA and ED is vertical OB.

Therefore, the angle ECO= the angle edo = 90 (vertically defined).

Because OE is the bisector of the angle AOB.

So angle COE= angle DOE (angle bisector definition)

Because in triangle COE and triangle DOE

Anglecoco = angledo (certification)

Angle COE= Angle DOE (authentication)

OE=OE (male * * * side)

So the triangle COE is equal to the triangle DOE(AAS)

So OC=OD (the angles corresponding to congruent triangles are equal).

3. Solution:

Because triangle COE is equal to triangle DOE (proved)

So CE=DE (congruent triangles's corresponding angles are equal).

So OE is the midline of the line segment CD (the points with the same distance to both ends of the line segment are all on the midline of this line segment).