Considere as matrizes A e B a seguir.
\( A=\left[\begin{array}{cccc}1 & 2 & \text{sen}\,x & \text{sen}\,2x\\3 & 4 & \text{sen}\,3x & \text{sen}\,4x\\5 & 6 & \text{sen}\,5x & \text{sen}\,6x\\7 & 8 & \text{sen}\,7x & \text{sen}\,8x\end{array}\right];\ B=\left[\begin{array}{cc}\cos x & -2\\-1 & 1\\0 & 2\cos x\\2\cos x & 1\end{array}\right] \)
O elemento C12 da matriz C = A∙B é igual a:
