Since $\displaystyle \cos(i)$ is a real number (1.54308...)

Does this mean that I can substitute "i" as follows?

$\displaystyle i=\arccos(1.54308...)$

If not, why not?

Also, since $\displaystyle i^i=\frac{1}{e^\frac{\pi}{2}}$ does this mean that

$\displaystyle i=\arccos(1.54308...)=\left(\frac{1}{e^\frac{\pi}{ 2}}\right)^\frac{1}{i}$

?