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Parallel Lines and Transversals . Honors Geometry Chapter 3, Section 1. Notes . What does it mean for two lines to be parallel? Parallel lines: Lines that do not intersect and are coplanar . What about lines that don’t intersect and aren’t coplanar?
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Parallel Lines and Transversals Honors Geometry Chapter 3, Section 1
Notes • What does it mean for two lines to be parallel? • Parallel lines: Lines that do not intersect and are coplanar. • What about lines that don’t intersect and aren’t coplanar? • Skew Lines: Lines that do not intersect and are not coplanar. • What does it mean for two planes to be parallel? • Parallel Planes:planes that do not intersect. • Example: the planes containing the ceiling and floor are parallel
Notes • Transversal: a line that intersects two or more lines in a plane at different points. • E.g. Line c is a transversal to lines a and b. • Line b is a transversal to which two other lines? • a & c • How about line a? • b & c • When a transversal intersects two lines, how many angles are formed? • 8 angles are formed
Notes • Angles formed by a transversal. • We give certain pairs of these angles special names. • Corresponding Angles: 1 & 5 ; 2 & 6 ; 3 & 7 ; 4 & 8 • Exterior Angles: 1, 2, 7, & 8 • Interior Angles: 3, 4, 5, 6 • Alternate Exterior Angles: 1 & 7 ; 2 & 8 • Alternate Interior Angles: 3 & 5 ; 4 & 6 • Consecutive Interior Angles: 4 & 5 ; 3 & 6
Notes • Symbols for parallel in statements and figures • The symbol ll means is parallel to • The pink arrows on lines PQ and RS indicate that they are parallel.
Angle Pair Names Activity • Using about ¼ of a piece of binder paper, draw three lines so that one intersects two of the others. • Color the exterior angles all one color • Color the interior angles all one color • Label the exterior and interior angles • Using another ¼ of a piece of binder paper, draw three lines so that one intersects two of the others. • Color each pair of corresponding angles a different color. • Label this quarter sheet of paper “corresponding angles.” • Using another ¼ of a piece of binder paper, draw three lines so that one intersects two of the others. • Color each pair of alternate exterior angles a different color. • Color each pair of alternate interior angles a different color. • Label this quarter sheet “alternate exterior and interior angles.” • Using the final ¼ of a piece of binder paper, draw three lines so that one intersects two of the others. • Color each pair of consecutive interior angles a different color. • Label this quarter sheet “consecutive interior angles.