Chapter 3 Flashcards
parallel lines
coplanar lines that do not intersect
skew lines
non coplanar lines that are not parallel nor intersecting
parallel planes
planes that do not intersect
theorem 3-1
if 2 parallel lines are cut by a third plane, then the lines of intersection are parallel
transversal
line that intersects two or more coplanar lines in unique points
alternate interior angles
two nonadjacent interior angles on opposite sides of the transversal
same-side interior angles
two interior angles on the same side of the transversal
corresponding angles
two angles in corresponding positions relative to the two lines
theorem 3-2
if two parallel lines are cut by a transversal, then alternate interior angles are congruent
theorem 3-3
if two parallel lines are cut by a transversal, then same-side interior angles are supplementary
theorem 3-4
if a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other one also
postulate 11
if two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel
theorem 3-5
if two lines are cut by a transversal and alternate interior angles are congruent, then the lines are parallel
theorem 3-6
if two lines are cut by a transversal and same-side interior angles are supplementary, then the lines are parallel
theorem 3-7
in a plane two lines perpendicular to the same line are parallel
theorem 3-8
through a point outside a line, there is exactly one line parallel to the given line
theorem 3-9
through a point outside a line, there is exactly one line perpendicular to the given line
theorem 3-10
two lines parallel to a third line are parallel to each other
scalene triangle
no sides congruent
isosceles triangle
at least two sides congruent
equilateral triangle
all sides congruent
acute
three acute angles
obtuse
one obtuse angle
right
one right angle