Prove the following statements indirectly.

**Problem : **

Given:

Triangle ABC is an isosceles triangle with base AC.Prove:

Segment BE is a median.

Segment BE is an angle bisector.

**Problem : **

Given: Circle F is inscribed in triangle ABC.

Prove: Angle DCF is congruent to angle ECF.

**Problem : **
Use indirect reasoning to explain why a triangle cannot have more than one
obtuse angle.