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 B Line 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 D Ray 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

Angles are defined by 3 points. X Z Y XYZ

These angles can be right angles. 90 

These angles can be right angles. c R S T U V RST = 90 ⁰ USR = 90 ⁰ USV = 90 ⁰ TSV = 90 ⁰

When lines intersect to form right angles, they are said to be perpendicular. V R T U c S UTRV

Lines can intersect to form acute and obtuse angles. 135  obtuse 45  acute

Lines can also run into each other to form straight angles.

180  is a straight angle

Lines do not always intersect.

Lines can be parallel.

Parallel lines have the same slope or steepness.

Lines can be… intersecting perpendicular 90º parallel skew

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.

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

The end.