User:HAHA VENOM

Remote Interior Angle Theorem
The measure of the exterior angle of a triangle is equal to the sum of the measures of the other two remote interior angles.



Given: In ∆ABC, angle ACD is the exterior angle.

To Prove: mACD=mABC+mBAC

Proof:

Hence, proved.

Isosceles Triangle Theorem
If two sides of a triangle are congruent, then the angles opposite to them are congruent.



Given: In ∆ABC, Side ABSide AC.

To Prove: ABCACB.

Construction: Draw the bisector of BAC, intersecting Side BC in point D.

Proof:

Hence, proved.