Theorems: Parallel Lines and Planes Flashcards
3-1
If two parallel lines are cut by a third plane, then the lines of intersection are parallel.
3-2
If two parallel lines are cut by a transversal, then alternate interior angles are congruent
3-3
If two parallel lines are cut by a transversal, then same-side interiror angles are supplementary.
3-4
If a transversal is perpendicular to one of two parallel lines, then it is perpendiccular to the other one also.
3-5
If two lines are cut by a transversal and alternate interior angles are congruent, then the two lines are parallel.
3-6
If two lines are cut by a transversal and same-side interiror angles are supplementry, then the two lines are parallel.
3-7
in a plane two lines perpendicular to the same line are parallel
3-8
Through a point outside a line, there is exactly one line parallel to the given line
3-9
Through a point outside a line, there is exactly one line perpendicular to the given line
3-10
two lines parallel to a third line are parallel to each other.
3-11
The sum of the measures of the angles of a triangle are 180.
3-11 C-1
If two angles of one triangle are congruent to two angles of another triangle, then the third angles are congruent
3-11 C-2
each angles of an equiangular triangle has measure of 60
3-11 C-3
In a triangle, there can be at most one right angle or obtuse angle.
3-11 C-4
The acute angles of a right triangle are complementary.
