Pre Algebra ( period 1)

Introduction to Geometry: Points, Lines, & Planes 9-1
Point:(symbol is a dot or just a letter) Location in space - no size
Ray: (arrow pointing to the right) - one endpoint and one direction- Named by its endpoint first
Line: (generally, line with arrows on both ends above 2 points on the line) - Series of points that goes on infinitely in both directions - named either direction
Line segment: (a line with no arrows on either end) - a piece of a line with 2 endpoints in either direction
Lines can be parallel (2 vertical lines) or intersecting in the same plane
Parallel lines are lines in the same plane that never meet
If they intersect at exactly 90 degrees, then they are perpendicular
If they don't intersect but are in two different planes, they are skew

Angle Relationships & Parallel Lines 9-2
angle: (angle opening to the right) two rays that meet at the same endpoint
named by either just the vertex, or 3 points on the angle in either direction with vertex in middle
adjacent angles share one ray
vertical angles are opposite each other and congruent (equal)
Complementary sum to 90 degrees and
supplementary sum to 180 degrees
acute is greater than 0 and less than 90
90 degrees is right angle
obtuse is greater than 90 but less than 180
180 is a straight angle (line)
to write the measure of an angle you write m<
Transversal: a line that intersects two other lines

Corresponding angles are formed by this transversal
These angles are on the same side of the transversal and also are both above or both below the line
When the two lines that are intersected are parallel, corresponding angles are congruent

Alternate interior angles are between the two lines (inside the two lines) and on opposite sides of the transversal (alternate sides) These angles are also congruent if the lines are parallel.

Same side interior: If angles are both inside and on the same side of the transversal, they are supplementary (sum to 180 degrees)

You can have lots of corresponding angles if you have a transversal intersecting more than 2 parallel lines - in fact they would be infinite if you kept adding another parallel line!
It's amazing that by just knowing one angle, you know all 8 angles with one transversal and two parallel lines! (I will show this in class on Tuesday!)