e^i*1.5708

e^i*1.5708 ?

$$\boxed{
\mathrm{e}^{\mathrm{i}\,\varphi} = \cos\left(\varphi \right) + \mathrm{i}\,\sin\left( \varphi\right)
}$$

$$\varphi= \frac{\pi}{2}=1.57079632679$$

$$\mathrm{e}^{\mathrm{i}\,\cdot1.57079632679 }=
\mathrm{e}^{\mathrm{i}\,\cdot\frac{\pi}{2} } = \cos\left(\frac{\pi}{2}\right) + \mathrm{i}\,\cdot\sin\left( \frac{\pi}{2}\right)\\
= 0 + \mathrm{i}\,\cdot1\\
= \mathrm{i}\\$$

e^i*1.5708  = i

Thanks Heureka,