Proofs

segment bisector/midpoint

divides a segment into 2 ≅ segments

angle bisector

divides an angle into 2 ≅ angles

vertical angles/right angles

angles are ≅

complementary angles

2 or more angles whose sum is 90°

supplementary angles

2 or more angles whose sum is 180°

isosceles triangle

a triangle with 2 ≅ legs and base angles

perpendicular lines

form ≅ right angles

parallel lines

lines cut by a transversal form ≅ alternate interior/corresponding angles

median

divides a segment into 2 ≅ segments(meets at the
midpoint)

altitude

is perpendicular to the base