===== Tangens =====
==== Function ====
>todo

$\tan(x):=\dfrac{\sin(x)}{\cos(x)}$

$\tan(x)=\sum_{n=1}^\infty (-1)^{n-1}\frac{2^{2n} (2^{2n}-1)}{(2n)!}B_{2n}\,x^{2n-1}$

with $B_k$ ... Bernoulli numbers
 
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=== Theorems ===
^ $\left(\dfrac{\tan(x)}{x}\right)^m=1+m\dfrac{1}{3}x^2+m\left(\dfrac{m}{18}+\dfrac{7}{90}\right)x^4+{\mathcal O}(x^6)$ ^

=== References ===
Wikipedia: 
[[https://en.wikipedia.org/wiki/Trigonometric_functions#tangent|Trigonometric_functions#tangent]]

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=== Related ===
[[Exponential function]],
[[Arcus Tangens]]