Both $K=\mathbb{Q}(\sqrt[3]{2},\zeta)$ and $L=\mathbb{Q}(\sqrt[3]{2},\sqrt{3})$ have degree $6$ over $\mathbb{Q}$. But the latter is obviously real, so $K\
eq L$, and in particular $\sqrt{3}\
otin K$.
Now, if $i\in K$, can we show that $\sqrt{3}\in K$ for a contradiction?