cac ki hieu trong toan hoc \(\sqrt{\sqrt[]{}\frac{ }{ }\hept{\begin{cases}\\\end{cases}}\orbr{\begin{cases}\\\end{cases}}^{ }^2_{ }|^{ }_{ }\widehat{ }\widebat{ }\cos\tanh\cosh\sinh\tan\sin\cot\Leftrightarrow\Rightarrow\Leftarrow\rightarrow\leftarrow\leftrightarrow\uparrow\downarrow\ne=\subset\supset\notin\exists\le\ge\forall⋮⊥\subseteq\supseteq\approx\in\lambda\pi\Phi\mu}\)