Let \( \vec{a} \) and \( \vec{b} \) be the vectors along the diagonals of a parallelogram having area \( 2\sqrt{2} \). Let the angle between \( \vec{a} \) and \( \vec{b} \) be acute, \( |\vec{a}| = 1 \), and \( |\vec{a} \cdot \vec{b}| = |\vec{a} \times \vec{b}| \). If \( \vec{c} = 2\sqrt{2}\,(\vec{a} \times \vec{b}) - 2\vec{b} \), then an angle between \( \vec{b} \) and \( \vec{c} \) is
