.
$$\sin \alpha + \sin \beta = 2\sin\frac{\alpha + \beta}{2}\cos\frac{\alpha-\beta}{2}$$
$$\sin \alpha - \sin \beta = 2\cos\frac{\alpha + \beta}{2}\sin\frac{\alpha-\beta}{2}$$
$$\cos \alpha + \cos \beta = 2\cos\frac{\alpha + \beta}{2}\cos\frac{\alpha-\beta}{2}$$
$$\cos \alpha - \cos \beta = 2\sin\frac{\alpha + \beta}{2}\sin\frac{\alpha-\beta}{2}$$
$$\left \lbrace \sum_{i=0}^n i^3 = \frac{(n^2+n)(n+6)}{9} \right \rbrace$$
$$ \lbrace \sum_{i=0}^n i^3 = \frac{(n^2+n)(n+6)}{9} \rbrace$$
$$\begin{array}{c|lcr}
n & \text{Left} & \text{Center} & \text{Right} \\
\hline
1 & 1.97 & 5 & 12 \\
2 & -11 & 19 & -80 \\
3 & 70 & 209 & 1+i \\
\end{array}$$
$$\left[
\begin{matrix}
V_A \\
V_B \\
V_C \\
\end{matrix}
\right] =
\left[
\begin{matrix}
1 & 0 & L \\
-cosψ & sinψ & L \\
-cosψ & -sinψ & L
\end{matrix}
\right]
\left[
\begin{matrix}
V_x \\
V_y \\
W \\
\end{matrix}
\right] $$