\input amstex

$$\align
1-\frac{e^{\hbox{\tiny\pmb i}336t}+e^{-\hbox{\tiny\pmb i}336t}}2=1\;\Longleftrightarrow\;\frac{2-\bigl(e^{\hbox{\tiny\pmb i}336t}+e^{-\hbox{\tiny\pmb i}336t}\bigr)}{2}=\frac 22
\endalign$$
\bye