Post on 14-Jan-2016
Points, Lines, and Planes
A point is an exact location in space.
You are here.
A true point has no length, no width, and no height.
In fact, you cannot see a true point.
A point is named by a letter.
P
Point P
Lines are 1-dimensional objects that have only length. Lines
continue forever in both directions.
Because a line has no width or height, you cannot see a true line.
A line is defined by 2 points.
A
BLine AB
A ray has a starting point but no ending point.
A ray of light has a starting point (like the sun) and continues
forever in the same direction.
Of course, if the ray hits an object, the light could be
absorbed or reflected.
MIRROR
A ray is also defined by 2 points.
C
DRay CD
A line segment has a starting point and an ending point. Line
segments can be measured.
A line segment also defined by 2 points.
E
F Line Segment EF
Lines can do various things.
Lines can intersect at a point to form angles.
X
Y
Z
When lines intersect to form right angles, they are said to be perpendicular.
V
R
TU
cS
UT RV
Lines do not always intersect.
Lines can be parallel.
Parallel lines have the same slope or steepness.
Is it possible for lines not to intersect and not be parallel
either?
Believe it or not, this is possible.Let’s consider a 3-dimensional
rectangular prism.
These 2 lines are not parallel, but they are not intersecting either.
These lines are called skew lines.
You might have heard the word “skewer” the last time you had a
barbecue.
S
K
E
W
E
R
A skewer raises your “dinner” off the surface of the grill. The skewer does not intersect the grill, and the skewer is not
parallel to the grill.
Lines can be…
intersecting
perpendicular
90º
parallelskew
A plane
is a flat
surface that has
length & width
but no height.
You can see a plane only if you view it at a certain angle.
A true plane goes on forever in all directions.
A true plane goes on forever in all directions.
A true plane goes on forever in all directions.
A true plane goes on forever in all directions.
A true plane goes on forever in all directions.
Planes can…
Planes can intersect.
An X-Wing fighter from Star Wars has wings that intersect.
Planes can be perpendicular.
Planes can be parallel.
A Tie Fighter from Star Wars has wings that are parallel.
Planes can be…intersecting
perpendicular
parallel