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Mathematics
Problem
The number of diagonals of an
n
n
n
-sided polygon is given by the formula
D
=
n
2
(
n
−
3
)
D = \frac{n}{2}(n - 3)
D
=
2
n
(
n
−
3
)
. A polygon has 90 diagonals. How many sides does it have?
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