Lesson 1 of 14
Cross once, or never cross
Show on a big screenTwo rails run off into the distance. Do they ever touch?
Step 1 of 4
- Two lines are drawn inside a page.
- Follow both lines past the edge.
- Far out, they meet at one point.
- Two lines with the same tilt never meet at all.
The rule
No. Rails keep the same distance apart, so they never touch.
Two straight lines on a flat page can do only two things. They can meet at one point. That point is where the lines intersect. Or they never meet, however far you follow them.
There is no third case. Only one straight line passes through two different points. So two lines sharing two points are just one line, drawn twice.
Slide the tilt. Watch where the lines meet.
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Try the lab to finish this lesson.