1 problem found
Show that if at least one of the four angles \(A\pm B\pm C\) is a multiple of \(\pi\), then \begin{alignat*}{1} \sin^{4}A+\sin^{4}B+\sin^{4}C & -2\sin^{2}B\sin^{2}C-2\sin^{2}C\sin^{2}A\\ & -2\sin^{2}A\sin^{2}B+4\sin^{2}A\sin^{2}B\sin^{2}C=0. \end{alignat*}