Prove $\left|\begin{smallmatrix} \sin^2x&\cot x&1\\ \sin^2y&\cot y&1\\ \sin^2z&\cot z&1 \end{smallmatrix}\right|=0$ if $x+y+z=\pi$
If $A$, $B$ and $C$ are the angles of a triangle then find the value of $\Delta$