Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

 B C

Notes for Session 4, Part B

 Note 2 Discuss or reflect on why "in the same plane" is an important part of the definition. If you think in three dimensions, two lines can never intersect but also be not parallel. To demonstrate this, you can draw a line on one piece of paper, then draw a line on another piece of paper. Put one of the pieces of paper on a table or desk, and hold the second one above the first, parallel to it. You can rotate the second piece of paper and see that the two lines will never intersect as long as the planes (papers) stay parallel, but the lines are not always parallel to each other.

 Note 3 If you are working in a group, you can also demonstrate this for the whole group with an overhead projector. Make two copies of the j, k, l setup on transparencies. Place both transparencies on the overhead projector, one on top of the other. Then slide the top transparency, keeping one line j on top of the other. Lines k and l very convincingly match up.