Theorem

• If two angles form a linear pair, then they are supplementary.

  Linear pair Theorem
• If two angles are supplements of the same angle, then they congruent.

  Congruent supplements theorem
• If two angles are complements of the same angle, then they are congruent.

  Congruent complements theorem
• All right angles are congruent

  Right angle congruence theorem
• Vertical angles are equal in measure.

  Vertical angles theorem
• If two congruent angles are supplementary, then each is a right angle

  Theorem
• If a point is on the bisector of an angle then it is equidistant from the sides of the angle

  Angle bisector theorem
• If a point in the interior of an angle is equidistant from the side of the angle, then it is on the bisector of the angle 


  Converse of the angle bisector theorem
• Located ⅔ of the distance from each vertex to the midpoint of two opposite side.


  Centroid theorem
• It is parallel to a side of triangle and it's length is half the length of that side.

  Triangle midsegment theorem