Vector Algebra

If \(\mathbf{a}\) and \(\mathbf{b}\) are two vectors such that \(\frac{\mathbf{a} \cdot \mathbf{b}}{|\mathbf{a}||\mathbf{b}|} < 0\) and \(|\mathbf{a} \cdot \mathbf{b}|=|\mathbf{a} \times \mathbf{b}|\) then the angle between the vectors \(\mathbf{a}\) and \(\mathbf{b}\) is