$\cot {16}^0\cot {44}^0+\cot {44}^0\cot {76}^0-\cot {76}^0\cot {16}^0=$______

$\begin{array}{l}\frac{\tan {76}^{\circ }+\tan {16}^{\circ }-\tan {44}^0}{\tan {16}^{\circ }\cdot \tan {44}^0\tan {76}^0}\\ =\frac{\mathrm{ta}{16}^{\circ }+\tan \left({60}^{\circ }+{16}^{\circ }\right)-\tan \left({60}^{\circ }-{16}^{\circ }\right)}{\tan {16}^{\circ }\cdot \tan \left({60}^{\circ }-{16}^{\circ }\right)\tan \left({60}^{\circ }+{16}^{\circ }\right)}\\ =\frac{3\tan 3\left({16}^{\circ }\right)}{\tan 3\left({16}^{\circ }\right)}=3\end{array}$