====== memo ======

$$x_{n+1}=x_n-\mathbb{\nabla}f(x_n)$$

$$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$

$$ x^y $$
$$ x_1 $$

$$ x_1^{abc} $$
$$ x_{123} $$

$$ \int^b_af(x)\mathrm{d}x $$

$$ \lim_{n\to{\infty}}f(n) $$

$$ \sum_{n=1}^{\infty}n $$

$$ \pm\frac{1}{2} $$

$$ \sqrt{x^2} = x $$

$$ \sqrt[3]{x^3} = x $$

$$ \left(\frac{a}{b}\right)^n $$

$$ \begin{pmatrix}
           a&b\\
           c&d\\
                  \end{pmatrix}^n $$
                  
$$ \begin{vmatrix}
           a&b\\
           c&d\\
                  \end{vmatrix} $$
                  
$$ \sin2\pi = 0 $$
$$ \cos{\frac{\pi}{3}} = \frac{\sqrt{3}}{2}$$

$$ \Delta $$
$$ \pi $$
$$ \lambda $$

$$ sin $$
$$ \mathrm{sin} $$

$$ x $$
$$ \mathbf{x} $$
$$ \boldsymbol{x} $$

$$ \mathbb{R} $$
$$ \mathbb{C} $$
$$ \mathbb{Z} $$


$$ \mathbb{Z} = \{x|x\mbox{は整数}\} $$

$$ \sqrt[5]{x^4} $$