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1. If two lines are parallel,
each pair of corresponding angles are congruent. Also
converse.
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2. If two lines are parallel,
each pair of alternate interior angles are congruent. Also
converse.
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3. If two lines are parallel,
each pair of interior angles on the same side of the
transversal are supplementary. Also converse.
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4. Two lines are parallel if
they are perpendicular to the same line.
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5. If a line is perpendicular to
one of two parallel lines, then it is also perpendicular to
the other.
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6. The sum of the measures of
the three angles of a triangle is 180.
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7. The measure of an exterior
angle of a triangle equals the sum of the measures of the
two non-adjacent interior angles.
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8. The sum of the measures of
the acute angles of a right triangle is 90 (complementary).
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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.
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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.
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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.
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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.
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13. An equilateral triangle is equiangular: 60-60-60. Also converse.
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14. Isosceles triangle: If two sides of
a triangle are congruent, the angles opposite these sides are
congruent. Also converse.
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15. Right triangle 45-45-90:
the measure of either leg equals one-half the measure of the
hypotenuse time
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16. Right triangle 30-60-90:
the measure of the side opposite the 30 angle is one-half the
measure of the hypotenuse.
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