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If two parallel planes are cut by a third plane,

then the lines of intersection are parallel

alternate interior angles

two nonadjacent interior angles on opposite sides of the transversal

Same side angles

two interior angles on the same side of the transversal

corresponding angles

two angles in corresponding positions relative to the two lines

If two parallel lines are cut by a transversal,

then corresponding angles are congruent

If two parallel lines are cut by transversal,

then alternate interior angles are congruent

If two parallel lines are cut by a transversal,

then same side interior angles are supplementary

If a transversal is perpendicular to one of two parallel lines,

then it is perpendicular to the other one also

If two parallel lines are cut by a transversal,

then correspondung angles are congruent

If two lines are cuy by a transversal and corresponding angles are congruent,

then the lines are parallel

If two lines are cuy by a transversal and alternate interioir angles are congruent,

then the lines are parallel

If two lines are cut by a transversal and same side interior angles are supplementary,

then the lines are parallel

In a plane two lines perpendicular to the same line

are parallel

Through a point outside a line,

there is exactly one line parallel to the given line

Through a point outside a line,

there is exactly on eline perpendicular to the given line

Two lines parallel to a third line

are parallel to each other

Scalene

no sides congruent

isosceles

at least two sides congruent

acute

three acute angles

obtuse

one obtuse angle

right

one right angle

equiangular

all angles congruent

The sum of the measure of the angles

of a triangle is 180

If two angles of one triangle are congruent to two angles of another triangle,

the the thrid angles are congruent

The acute angles of a right triangle

are complementary

The measure of an exterior angles of a triangle equals

the sum of measures of the two remote interioir angles

The sum of the meausre of angles or a convex polygon with n sides

is (n-2)180.

The sum of the measures of the exterior angles of any convex polygon,

one angle at each vertex, is 360