1. If two lines are parallel,
each pair of corresponding angles are congruent. Also
converse.


2. If two lines are parallel,
each pair of alternate interior angles are congruent. Also
converse.

3. If two lines are parallel,
each pair of interior angles on the same side of the
transversal are supplementary. Also converse.


4. Two lines are parallel if
they are perpendicular to the same line.

5. If a line is perpendicular to
one of two parallel lines, then it is also perpendicular to
the other.



6. The sum of the measures of
the three angles of a triangle is 180.


7. The measure of an exterior
angle of a triangle equals the sum of the measures of the
two nonadjacent interior angles.

8. The sum of the measures of
the acute angles of a right triangle is 90 (complementary).


9. Triangle Congruence S.A.S. If two
sides and the included angle of one triangle are congruent to
the corresponding parts of another, then the triangles are
congruent.

10. Triangle Congruence A.S.A. If two
angles and the included side of one triangle are congruent to
the corresponding parts of another, then the triangles are
congruent.


11. Triangle Congruence S.S.S. If
three sides of one triangle are congruent to the three sides of
a second triangle, then the triangles are congruent.

12. Right Triangle Congruence. Two
right triangles are congruent if the hypotenuse and a leg of one
triangle are congruent to the corresponding parts of the other
triangle.


13. An equilateral triangle is equiangular: 606060. Also converse.

14. Isosceles triangle: If two sides of
a triangle are congruent, the angles opposite these sides are
congruent. Also converse.


15. Right triangle 454590:
the measure of either leg equals onehalf the measure of the
hypotenuse time
.

16. Right triangle 306090:
the measure of the side opposite the 30 angle is onehalf the
measure of the hypotenuse.


