Vector Algebra

If \(\overline{\mathrm{a}}\) and \(\overline{\mathrm{b}}\) are two unit vectors such that \(\overline{\mathrm{a}}+2 \overline{\mathrm{b}}\) and \(5 \bar{a}-4 \bar{b}\) are perpendicular to each other, then the angle between \(\bar{a}\) and \(\bar{b}\) is