If vectors $\overrightarrow{A}$ = cos $\omega$t i$\hat{l}$ + sin$\omega$t $\hat{j}$ and $\overrightarrow{B}$ = cos $\frac{\omega t}{2}$ $\hat{l}$ + sin $\frac{\omega t}{2}$ $\hat{j}$ are functions of times, then the value of t at which they are orthogonal to each other is: