A diagonal of a polygon is a line segment that connects two nonadjacent vertices. A triangle has no diagonals. A quadrilateral has two diagonals. How many diagonals are in a pentagon? How many are in a hexagon? Write an equation to represent the number of diagonals,d, in polygons with n sides.

Question

anonymous · Answer

|dw:1363467481088:dw|
for 1 vertex to N-3 vertices, 
and there are n such vertices.
Now, each diagonal has been counted twice

anonymous · Answer

|dw:1363467688624:dw|

anonymous · Answer

Thank you very much

directrix · Answer

> Write an equation to represent the number of diagonals,d, in polygons with n sides.

If n is the number of side of the convex polygon, then the number of diagonals of the polygon is the following:  n*(n-3)/2.

anonymous · Answer

thats what I said! in my first post. the student has to do some minor work. no spoon feeding

directrix · Answer

>for 1 vertex to N-3 vertices, 
and there are n such vertices.

Now, each diagonal has been counted twice
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I did not recognize the above ^^ (especially the initial two sentence fragments) as the beginning of an answer to this question:  Write an equation to represent the number of diagonals,d, in polygons with n sides.