Unit 2B - Proofs & Justifications

  • The sum of all the interior angles of a triangle sum to 180

  • The sum of all the angles that form a line is 180

  • If 2 parallel lines are cut by a transversal, then alternate interior angles are congruent

  • The acute angles of a right triangle are complementary

  • All right angles measure 90

  • An exterior angle of a triangle is equal to the sum of the 2 non-adjacent interior angles

  • Linear pairs are supplementary

  • If 2 sides of one triangle are congruent, the angles opposite them are also congruent

  • If 2 angles of one triangle are congruent, the sides opposite them are also congruent

  • The largest angle will always be opposite to the longest side

  • The shortest side is opposite the smallest angles

  • Triangle theorem: The sum of the 2 smallest sides must be greater than the largest side

  • ***Substitution in step proofs are allowed***