Geometry - Line Segments, Rays, and Angles

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     Students generally don’t equate ‘lines’ with geometry.  It’s interesting to note that most shapes consist of lines.  Angles are also made from lines.  In fact, there is a section of geometry that only deals with lines.

     Lines have several characteristics and definitions.  A line segment is a straight line segment which is part of the straight line between two points.  The points on each side of the line segment are referred to as the end points.  A ray is the part of the line which consists of the given point and the set of all points on one side of the end point.  An angle can be defined as two rays or two line segments having a common end point. The endpoint becomes known as the vertex. An angle occurs when two rays meet or unite at the same endpoint.  A transversal, or a line that intersects two or more coplanar lines, each at a different point, is a very useful line in geometry.  Transversals tell us a great deal about angles.

     When two lines intersect and form a right angle, they are perpendicular to one another.  Perpendicular angles (which look like an inverted letter’t’) result in a right angle. 
 
     When lines run on infinitely and never meet, and are always the same distance apart from each other, they are called parallel lines.  So, if two lines started off near each other but began to slant forwards, they would eventually meet and not be considered parallel.
 
     When parallel lines are intersected by other lines then angles are formed.  If a third line intersects two parallel lines perpendicularly, we get two sets of four right angles.  If a third line intersects the parallel lines and is not perpendicular, there is an acute angle formed and an obtuse angle formed.

     A thorough understanding of these concepts will help students in all areas of geometry.

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Tutorgiant.com provides Line lessons with worksheets.

See some of the lessons in our video library.

ANGLES - Lesson (D) Intersecting Lines and Measuring Angles (Grade 8)

BISECTORS - Lesson (B) Segment Bisectors (Grades 9-10)

BISECTORS - Lesson (A) Angle Bisectors (Grades 9-10)
BISECTORS - Lesson (B) Segment Bisectors (Grades 9-10)
LINES - Parallel, Perpendicular, and Intersecting Lines (Grades 7-8)

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by Stuart Ackerman        

     MSc.Ed.,B.A.