1-28 Conjectures Geometry ZAHN

If two angles form a linear pair, then the measures of the angles add up to 
180°

If two angles are vertical angles, then they are congruent (have equal 
measures)

If two parallel lines are cut by a transversal, then 
corresponding angles are congruent

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

If two parallel lines are cut by a transversal, then 
alternate exterior angles are congruent

If two parallel lines are cut by a transversal, then corresponding angles are 
congruent, alternate interior angles are congruent, and alternate exterior angles are congruent

If two lines are cut by a transversal to form pairs of 
congruent corresponding angles, congruent alternate interior angles, or congruent alternate exterior 
angles, then the lines are parallel

If a point is on the perpendicular bisector of a segment, then it is equidistant from the endpoints

If a point is equidistant from the endpoints of a 
segment, then it is on the perpendicular bisector of the segment

The shortest distance from a point to a line is measured along the perpendicular segment from the point to the line

If a point is on the bisector of an angle, then it is equidistant from the sides of the angle

The three angle bisectors of a triangle are concurrent (meet at a point)

The three perpendicular bisectors of a triangle are concurrent

The three altitudes (or the lines containing the altitudes) of a triangle are concurrent

The circumcenter of a triangle is equidistant from the vertices