De Wikipedia, le encyclopedia libere
Un summa [ 1] addition . Anque le resultato de un serie es un summa. Pro additiones longe e regular, on usa le symbolo
Σ
{\displaystyle \Sigma }
sigma .
Per exemplo,
∑
i
=
1
6
i
=
1
+
2
+
3
+
4
+
5
+
6
=
21
{\displaystyle \sum _{i=1}^{6}i=1+2+3+4+5+6=21}
In general, pro omne
n
∈
N
{\displaystyle n\in \mathbb {N} }
∑
i
=
1
n
i
=
n
(
n
+
1
)
2
{\displaystyle \sum _{i=1}^{n}i={\frac {n(n+1)}{2}}}
In le exemplo:
∑
i
=
1
6
i
=
6
(
6
+
1
)
2
=
6
⋅
7
2
=
42
2
=
21
{\displaystyle \sum _{i=1}^{6}i={\frac {6(6+1)}{2}}={\frac {6\cdot 7}{2}}={\frac {42}{2}}=21}
Un altere exemplo:
∑
i
=
1
100
i
=
100
(
100
+
1
)
2
=
5050
{\displaystyle \sum _{i=1}^{100}i={\frac {100(100+1)}{2}}=5050}
↑
Derivation (in ordine alphabetic):
(ca ) Sumatori ||
(de) Summe ||
(en) (es) (fr) (it) (pt) (ro ) Sumă
|| (ru) Сумма (математика)
