Flashcard Set: Angles Theorems & Pairs Front: Alternate Exterior Angles Back: Outside the lines, opposite sides of the transversal. Equal if lines are parallel. m∠A = m∠B Front: Alternate Interior Angles Back: Inside the lines, opposite sides of the transversal. Equal if lines are parallel. m∠A = m∠B Front: Complementary Angles Back: Two angles that add up to a right angle. m∠1 + m∠2 = 90° Front: Supplementary Angles Back: Two angles that add up to a straight line. m∠1 + m∠2 = 180° Front: Perpendicular Lines Back: Lines that make four right angles. Each angle = 90° Front: Same-Side Exterior Angles Back: Outside the lines, same side of transversal. Supplementary if lines are parallel. m∠1 + m∠2 = 180° Front: Same-Side Interior Angles Back: Inside the lines, same side of transversal. Supplementary if lines are parallel. m∠1 + m∠2 = 180° Front: Corresponding Angles Back: Same position on the lines (top-left with top-left). Equal if lines are parallel. m∠A = m∠B Front: Vertical Angles Back: Across from each other when lines cross. Always equal. m∠1 = m∠2 Front: Linear Pair Theorem Back: Two angles forming a straight line. m∠1 + m∠2 = 180° Front: Angle Bisector Theorem Back: A line splits an angle into two equal angles. m∠1 = m∠2 Front: Alternate Interior Angles Theorem Back: Alternate interior angles are equal if lines are parallel. m∠A = m∠B Front: Alternate Exterior Angles Theorem Back: Alternate exterior angles are equal if lines are parallel. m∠A = m∠B Front: Same-Side Interior Angles Theorem Back: Same-side interior angles are supplementary if lines are parallel. m∠1 + m∠2 = 180° Front: Same-Side Exterior Angles Theorem Back: Same-side exterior angles are supplementary if lines are parallel. m∠1 + m∠2 = 180° Front: Perpendicular Lines Theorem Back: Perpendicular lines make four right angles