Posted by Zack on Wednesday, October 8, 2008 at 1:18am.
We are learning about proofs. We drew lines between noncollinear points. Our table showed 2 points >> 1 line segment, 3 point >> 3 line segments, 4 points >> 6 line segments, 5 points >> 10 line seg, 6 points >> 15 line seg. etc.
Write an expression in terms of n for the number of line segments that can be drawn between n points.
Please help.

geometry  drwls, Wednesday, October 8, 2008 at 2:01am
1, 3, 6, 10,.. is the series
N*(N1)/2
where N is the number of points.
These are sometimes refered to as triangle numbers. (This of stacking pop cans in a triangle with rows of 1, 2, 3, 4 etc.)
See http://en.wikipedia.org/wiki/Triangular_numbers

geometry  maria, Friday, December 16, 2011 at 4:20pm
line segment 6cm and divide 5 congruent parts

geometry  Anonymous, Thursday, June 4, 2015 at 12:41pm
A circle is described by the equation x2 + y2 + 14x + 2y + 14 = 0. What are the coordinates for the center of the circle and the length of the radius?
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