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User:Superdan006
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Sandbox
π
=
4
∑
k
=
0
∞
(
−
1
)
k
2
k
+
1
{\displaystyle \pi =4\sum _{k=0}^{\infty }{\frac {(-1)^{k}}{2k+1}}}
(3)
2
π
=
∑
k
=
0
∞
(
−
1
)
k
(
4
k
+
1
)
∏
k
=
1
∞
2
k
−
1
2
k
{\displaystyle {\frac {2}{\pi }}=\sum _{k=0}^{\infty }(-1)^{k}(4k+1)\prod _{k=1}^{\infty }{\frac {2k-1}{2k}}}
(4)
f
(
x
)
=
∑
n
=
0
∞
f
(
n
)
(
x
)
n
!
(
x
−
a
)
n
{\displaystyle f(x)=\sum _{n=0}^{\infty }{\frac {f^{(n)}(x)}{n!}}(x-a)^{n}}
(5)
f
(
x
)
=
x
{\displaystyle f(x)={\sqrt {x}}}
(6)
f
(
x
)
=
1
+
x
=
∑
n
=
0
∞
(
−
1
)
n
(
2
n
)
!
(
1
−
2
n
)
(
n
!
)
2
x
n
4
n
{\displaystyle f(x)={\sqrt {1+x}}=\sum _{n=0}^{\infty }{\frac {(-1)^{n}(2n)!}{(1-2n)(n!)^{2}}}{\frac {x^{n}}{4^{n}}}}
(7)
f
(
x
)
=
N
2
+
x
=
∑
n
=
0
∞
(
−
1
)
n
(
2
n
)
!
(
1
−
2
n
)
(
n
!
)
2
x
n
4
n
N
2
n
−
1
{\displaystyle f(x)={\sqrt {N^{2}+x}}=\sum _{n=0}^{\infty }{\frac {(-1)^{n}(2n)!}{(1-2n)(n!)^{2}}}{\frac {x^{n}}{4^{n}N^{2n-1}}}}
(7)
x
1
=
x
0
−
f
(
x
0
)
f
′
(
x
0
)
{\displaystyle x_{1}=x_{0}-{\frac {f(x_{0})}{f'(x_{0})}}}
x
r
o
o
t
=
a
{\displaystyle x_{root}={\sqrt {a}}}
x
r
o
o
t
2
=
a
{\displaystyle x_{root}^{2}=a}
x
r
o
o
t
2
−
a
=
0
{\displaystyle x_{root}^{2}-a=0}
f
(
x
)
=
x
2
−
a
{\displaystyle f(x)=x^{2}-a}
f
′
(
x
)
=
2
x
{\displaystyle f'(x)=2x}
x
n
+
1
=
x
n
−
x
n
2
−
a
2
x
n
{\displaystyle x_{n+1}=x_{n}-{\frac {x_{n}^{2}-a}{2x_{n}}}}
x
=
q
0
+
p
1
q
1
+
p
2
q
2
+
⋱
{\displaystyle {\sqrt {x}}=q_{0}+{\cfrac {p_{1}}{q_{1}+{\cfrac {p_{2}}{q_{2}+\ddots \,}}}}}
x
=
a
+
b
2
a
+
b
2
a
+
⋱
{\displaystyle {\sqrt {x}}=a+{\cfrac {b}{2a+{\cfrac {b}{2a+\ddots \,}}}}}
d
d
x
[
(
1
−
x
2
)
d
d
x
P
n
(
x
)
]
+
n
(
n
+
1
)
P
n
(
x
)
=
0
{\displaystyle {d \over dx}\left[(1-x^{2}){d \over dx}P_{n}(x)\right]+n(n+1)P_{n}(x)=0}
P
0
(
x
)
=
1
{\displaystyle P_{0}(x)=1}
P
1
(
x
)
=
x
{\displaystyle P_{1}(x)=x}
P
n
+
1
(
x
)
=
1
n
+
1
x
P
n
(
x
)
−
n
P
n
−
1
(
x
)
{\displaystyle P_{n+1}(x)={\frac {1}{n+1}}xP_{n}(x)-nP_{n-1}(x)}
P
4
(
x
)
=
35
8
x
4
−
15
4
x
2
+
3
8
{\displaystyle P_{4}(x)={\frac {35}{8}}x^{4}-{\frac {15}{4}}x^{2}+{\frac {3}{8}}}
x
2
d
2
y
d
x
2
+
x
d
y
d
x
+
(
x
2
−
α
2
)
y
=
0
{\displaystyle x^{2}{\frac {d^{2}y}{dx^{2}}}+x{\frac {dy}{dx}}+(x^{2}-\alpha ^{2})y=0}
J
n
−
1
(
x
)
=
2
n
x
J
n
(
x
)
−
J
n
+
1
(
x
)
{\displaystyle J_{n-1}(x)={\frac {2n}{x}}J_{n}(x)-J_{n+1}(x)}
J
0
(
x
)
+
2
∑
n
=
1
∞
J
2
n
(
x
)
=
1
{\displaystyle J_{0}(x)+2\sum _{n=1}^{\infty }J_{2n}(x)=1}
x
r
o
o
t
=
l
o
g
2
(
a
)
{\displaystyle x_{root}=log_{2}(a)}
2
x
r
o
o
t
=
a
{\displaystyle 2^{x_{root}}=a}
2
x
r
o
o
t
−
a
=
0
{\displaystyle 2^{x_{root}}-a=0}
f
(
x
)
=
2
x
−
a
{\displaystyle f(x)=2^{x}-a}
f
′
(
x
)
=
l
n
(
2
)
2
x
{\displaystyle f'(x)=ln(2)2^{x}}
x
n
+
1
=
x
n
−
1
l
n
(
2
)
+
a
l
n
(
2
)
2
x
n
{\displaystyle x_{n+1}=x_{n}-{\frac {1}{ln(2)}}+{\frac {a}{ln(2)2^{x_{n}}}}}