Theorems 6-1 through 6-13
Theorem 6-9
Each diagonal of a rhombus bisects two angles of the rhombus
Theorem 6-3
The diagonals of a parallelogram bisect each other
Theorem 6-11
The diagonals of a rectangle are congruent
Theorem 6-10
The diagonals of a rhombus are perpendicular
Theorem 6-8
If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram
Theorem 6-7
If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram
Theorem 6-12
If one diagonal of a parallelogram bisects two angles of the parallelogram, then the parallelogram is a rhombus
Theorem 6-6
If one pair of opposite sides of a quadrilateral is congruent and parallel, then the quadrilateral is a parallelogram
Theorem 6-14
If the diagonals of a parallelogram are congruent, then the parallelogram is a rectangle
Theorem 6-13
If the diagonals of a parallelogram are perpendicular, then the parallelogram is a rhombus
Theorem 6-5
If the diagonals of a quadrilateral are both congruent and parallel, then the quadrilateral is a parallelogram
Theorem 6-4
If three or more parallel lines cut off congruent segments on one transversal, then they cut of congruent segments on every transversal
Theorem 6-2
Opposite angles of a parallelogram are congruent
Theorem 6-1
Opposite sides of a parallelogram are congruent