number of diagonals in an n-sided polygon is n(n-1)/2 - n
If the polygon has 12 sides, number of diagonals is 12(12-1)/2 -12
= (12)(11)/2 -12
= 132/2 - 12
= 66-12 = 54
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No. An isosceles trapezium (isosceles triangle with its apex removed) would have congruent diagonals but it is not a parallelogram.
54 Diagonals. * * * * * A polygon with n sides has 1/2*n*(n-3) diagonals. So a decagon would have 1/2*10*7 = 35 diagonals. How the Community answer got 54 is anybody's guess!
They might, but they do not have to. A very long and narrow parallelogram would have diagonals that cross at a very sharp angle.no they donot
No. If they were equal the rhombus would become a square.
An Octagon has 20 diagonals in total. There is actually a really simple formula to figuring out the diagonals in any polygon: (n-3) x (n/2). If we put 8 in there than it would be (8-3) x (8/2) - 5x4=20, so the answer is 20 diagonals.