Posted by karen on Sunday, February 10, 2013 at 7:45pm.
a diagonal of a polygon is a straight line joining any 2 nonadjacent corners.a decagon has 10 corners. .how many diagonals does it have ?

math  Reiny, Sunday, February 10, 2013 at 9:23pm
Joining any two points will produce a line
there are C(10,2) such lines or 45 of them
But, 10 of them will be the actual sides of the polygon, the others are diagonals
number of diagonals = 4510 = 35

math  karen, Monday, February 11, 2013 at 9:01am
thanks for your kindness
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