Vector Algebra

\(A, B, C, D\) are four points in a plane with position vectors \(\bar{a}, \bar{b}, \bar{c}, \bar{d}\) respectively such that \((\bar{a}-\bar{d}) \cdot(\bar{b}-\bar{c})=(\bar{b}-\bar{d}) \cdot(\bar{c}-\bar{a})=0\). The point \(D\), then is the ___________
of \(\triangle \mathrm{ABC}\)