October 29, 2015
HAPPY THURSDAY!!!
2.7/2.8 Segment and Angle Addition
Objective: Write proofs involving segment addition and segment relationships
Assignment: ALWAYS, SOMETIMES, NEVER & p. 139 #9-­‐12 & p. 140 #18 & p. 147 #1, 2, 17
October 29, 2015
The two planes meet at the edge which lies on line r.
If two planes intersect, the intersection is a line.
The points A and D both line on line p and in plane N.
If two points lie in a plane, then the entire line containing
those points lies in that plane.
Never; 3 noncollinear points determine a plane
Always; through any two points there is exactly one line
Always; a plane contains at least three points not on the same line, and each pair of
these determines a line.
October 29, 2015
Given: B is the midpoint of AC; C is the midpoint of BD
Prove: AB = CD
statements
reasons
B is the midpoint of AC
given
AB = BC
midpoint theorem
C is the midpoint of BD
given
BC = CD
midpoint theorem
AB = CD
transitive theorem
AB = CD
def. of congruency
October 29, 2015
Always; the intersection of two planes is a line, and a line contains at least 2 pts.
Sometimes; they might have only that single point in common (corner of a room) or
there might be an entire line if the intersection of the three planes is a line
If two points lie in a plane, then the entire line containing those
points lies in that plane.
If two lines intersect, then their intersection is exactly one point.
October 29, 2015
Given: E is the midpoint of AB and CD; AB = CD
Prove: AE = ED
statements
reasons
E is the midpoint of AB and CD
given
AE = 1/2 AB ; ED = 1/2 CD
defintion of midpoint
AB = CD
given
1/2 AB = 1/2 CD
multiplication prop. of eq.
AE = ED
substitution
AE = ED
def. of congruency