Geo Theorems

18 terms

vertical angles

if two lines intersect at a point, then their vertical angles are congruent

converse of alternate interior angles

if two lines are cut by a transversal forming congruent alternate interior angles, then the lines are parallel

parallel transivity

if two lines are parallel to a third line, then they are parallel to each other

alternate interior angles

if two parallel lines are cut by a transversal then the alternate interior angles are congruent.

perpendicular to parallel

if two lines in the same plane are perpendicular to a third line, then they are parallel to each other

interior supplements

if two parallel lines are cut by a transversal, then the interior angles on the same side of the transversal are supplementary

converse of interior supplements

if two lines are by a transversal forming interior angles on the same side of the transversal that are supp., then the lines are parallel

alternate exterior angles

if two parallel lines are cut by a transversal then the alternate exterior angles are congruent

converse of aea

if two lines are cut by a transversal forming alternate exterior angles, then the lines are parallel

isosceles triangle

if a triangle is isosceles, then its base angles are congruent

converse of isosceles triangle

if two angles of a triangle are congruent, then the triangle is isosceles

congruent and supp.

if two angles are both congruent+supplementary...

supplements of congruent angles

if two angles are congruent, then the supplements to those angles must also be congruent

triangle sum Tr

if a figure is a triangle, then the sum of the measures of the angles are 180

third angle third angle

if two angles of one triangle are congruent to two angles of another triangle, then the third angle in each triangle is congruent to the 3rd angle in the other triangle

Parallelogram Diagonal triangle

if you have a parallelogram then a diagonal divides the parallelogram into two congruent triangles

opposite sides

the opposite sides in a parallelogram are congruent

opposite angles

if a figure isn't a parallelogram then the opposite angles are congruent