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logarithms
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Logarithm
The logarithm of
x
is
y =
log
a
x
, with
x = a
y
.
x >
0
a >
0
a ≠
1
Graph
a ∈
(1; +∞)
a ∈
(0; 1)
logarithm
x
y =
log
a
x
0
a
0
1
a
1
1
a
2
2
a
3
3
a
0
1
a
−1
−1
a
−2
−2
a
−3
−3
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Enter
a
and 1 value
a =
x =
log
a
x =
Error:
a ≤
0
Error:
a =
1
Error:
x <
0
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Formulas
logarithm
$$ y = \log_a x \ \Longleftrightarrow \ x = a^y $$
$$ \begin{aligned} & \log_a x = \frac{\log_b x}{\log_b a} = \frac{\log x}{\log a} = \frac{\ln x}{\ln a} \\ \\ & \log_a x = \frac{1}{\log_x a} \end{aligned} $$
$$ \begin{aligned} & \log_a \left(x\cdot z\right) = \log_a x + \log_a z \\ \\ & \log_a \left(\frac{x}{z}\right) = \log_a x - \log_a z \end{aligned} $$
$$ \begin{aligned} & \log_a 1 = 0 \\ \\ & \log_a a = 1 \end{aligned} $$
$$ \begin{aligned} & \log_a x^r = r\cdot\log_a x \\ \\ & \log_a a^r = r \\ \\ & a^{\log_a x} = \log_a a^x = x \end{aligned} $$
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