Do you mean arccos, arcsin and arctan ?

If that's what you mean, press "2nd" then cos, sin or tan.

I already knew the answer.

But I rarely (not to say "never") submit questions when I don't already know the answer. It's just, as you said, "brain food"

Quelle est la question ?

$$\left\{ \begin{array}{l}{\mathtt{x}} = \left({\frac{\left(\left({\frac{\left({\sqrt{{\mathtt{3}}}}{\mathtt{\,\times\,}}{i}\right)}{{\mathtt{2}}}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)\right)}{\left({\mathtt{9}}{\mathtt{\,\times\,}}{\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}\right)}}\right){\mathtt{\,\small\textbf+\,}}{\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}{\mathtt{\,\times\,}}\left({\mathtt{\,-\,}}\left({\frac{\left({\sqrt{{\mathtt{3}}}}{\mathtt{\,\times\,}}{i}\right)}{{\mathtt{2}}}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)\\
{\mathtt{x}} = {\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}{\mathtt{\,\times\,}}\left(\left({\frac{\left({\sqrt{{\mathtt{3}}}}{\mathtt{\,\times\,}}{i}\right)}{{\mathtt{2}}}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)\right){\mathtt{\,\small\textbf+\,}}\left({\frac{\left({\mathtt{\,-\,}}\left({\frac{\left({\sqrt{{\mathtt{3}}}}{\mathtt{\,\times\,}}{i}\right)}{{\mathtt{2}}}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}\right)\right)}{\left({\mathtt{9}}{\mathtt{\,\times\,}}{\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}\right)}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)\\
{\mathtt{x}} = \left({\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{1}}}{\left({\mathtt{9}}{\mathtt{\,\times\,}}{\left(\left({\frac{{\sqrt{{\mathtt{356\,845}}}}}{{{\mathtt{3}}}^{\left({\frac{{\mathtt{3}}}{{\mathtt{2}}}}\right)}}}\right){\mathtt{\,\small\textbf+\,}}\left({\frac{{\mathtt{3\,104}}}{{\mathtt{27}}}}\right)\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}\right)}}\right){\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)\\
\end{array} \right\}$$

$${\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{2}} = {{\mathtt{2}}}^{{\mathtt{14}}} = {\mathtt{16\,384}}$$

$${\mathtt{9}}{\mathtt{\,\small\textbf+\,}}{\mathtt{10}} = {\mathtt{19}}$$

Exactly.

Here's your cookie :

The square root of a positive number n, is a number a which square is equal to n.

$${{\mathtt{a}}}^{{\mathtt{2}}} = {\mathtt{n}}$$

a% of n= $${\frac{{\mathtt{a}}{\mathtt{\,\times\,}}{\mathtt{n}}}{{\mathtt{100}}}}$$

So 35% of 100=$${\frac{{\mathtt{35}}{\mathtt{\,\times\,}}{\mathtt{100}}}{{\mathtt{100}}}} = {\mathtt{35}}$$

Twice as good as I expected: You've got

$$\textcolor[rgb]{1,0,0}{40/20}$$

CONGRATULATIONS !    

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