what type of lines are these?

Dr.Peterson said:
"Concurrent" just means intersecting in one point, and applies to any number of lines: https://mathworld.wolfram.com/Concurrent.html

It's most interesting when three or more lines are concurrent, as it is usual for any two lines to be concurrent (parallel lines being special): https://www.mathopenref.com/concurrent-lines.html

Wikipedia gives many such interesting examples: https://en.wikipedia.org/wiki/Concurrent_lines

Your source is not very well-written.
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Thanks for the comments and links. Really interesting!.
 
Dr.Peterson said:
"Concurrent" just means intersecting in one point, and applies to any number of lines: https://mathworld.wolfram.com/Concurrent.html

It's most interesting when three or more lines are concurrent, as it is usual for any two lines to be concurrent (parallel lines being special): https://www.mathopenref.com/concurrent-lines.html

Wikipedia gives many such interesting examples: https://en.wikipedia.org/wiki/Concurrent_lines

Your source is not very well-written.
Click to expand...
The article was written in Spanish. I just read it and put it into English.
 
eddy2017 said:
These definitions allow us to approach the notion of a concurrent line. Concurrent lines are three or more lines that are in the same plane and that have a common point. This means that the concurrent lines pass through the same point, unlike parallel lines that do not have points in common, they are equidistant from each other and do not have the possibility of crossing even when they are prolonged indefinitely. Both properties, therefore, are exclusive: if the lines are parallel, they are not concurrent, and vice versa".
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Among other issues:
  • There is no such thing as "a concurrent line"; the concept requires more than one line
  • It is not restricted to three or more lines; as I said, it can apply to two lines
  • Concurrent lines need not be in the same plane. (Think of the slanted edges of a pyramid.)
  • If you have three lines that are not concurrent, two of them might be parallel and the other not, or none of them may be parallel -- the "vice versa" applies only to two lines, but they excluded that possibility! The sides of a triangle are neither concurrent nor parallel.
This just is not written by a mathematician, who would think much more carefully.
 
Dr.Peterson said:
Among other issues:
  • There is no such thing as "a concurrent line"; the concept requires more than one line
  • It is not restricted to three or more lines; as I said, it can apply to two lines
  • Concurrent lines need not be in the same plane. (Think of the slanted edges of a pyramid.)
  • If you have three lines that are not concurrent, two of them might be parallel and the other not, or none of them may be parallel -- the "vice versa" applies only to two lines, but they excluded that possibility! The sides of a triangle are neither concurrent nor parallel.
This just is not written by a mathematician, who would think much more carefully.
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thank you, Dr Peterson. Grain to my mill all that you explained. sometimes i have to go to spanish sources cos my English is not that good. so thank for clarifying all that.
 
Dr.Peterson said:
"Concurrent" just means intersecting in one point, and applies to any number of lines: [Missing links/text have been left out for the quote box.]


Wikipedia gives many such interesting examples: https://en.wikipedia.org/wiki/Concurrent_lines
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The Wikipedia source in the link lists examples where the number of lines that are concurrent are almost all three or greater.
Someone reading that could come away thinking that three lines minimum are required for concurrency.
 
lookagain said:
The Wikipedia source in the link lists examples where the number of lines that are concurrent are almost all three or greater.
Someone reading that could come away thinking that three lines minimum are required for concurrency.
Click to expand...
And in fact, three lines are required for concurrency to be interesting (unless perhaps there is something else special about the point at which they concur). Also, most examples are in a plane.
 
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