Vector Algebra

If \(\overline{\mathrm{a}}, \overline{\mathrm{b}}, \overline{\mathrm{c}}\) are unit vectors and \(\theta\) is angle between \(\overline{\mathrm{a}}\) and \(\bar{c}\) and \(\bar{a}+2 \bar{b}+2 \bar{c}=\overline{0}\), then \(|\bar{a} \times \bar{c}|=\)