# Objective

is to represent equation array using LaTeX.

## Example 1.

### Code

$$\left. \begin{array}{lllll} \lambda_{11} & = & \cos(x'_1,x_1) & = & \cos\theta \\ \lambda_{12} & = & \cos(x'_1,x_2) & = & \cos \bigg( \frac{\pi}{2} - \theta \bigg) = \sin\theta \\ \lambda_{21} & = & \cos(x'_2,x_1) & = & \cos \bigg( \frac{\pi}{2} + \theta \bigg) = - \sin\theta \\ \lambda_{22} & = & \cos(x'_2,x_2) & = & \cos\theta \end{array} \right\}$$

### Result

$\left. \begin{array}{lllll} \lambda_{11} & = & \cos(x'_1,x_1) & = & \cos\theta \\ \lambda_{12} & = & \cos(x'_1,x_2) & = & \cos \bigg( \frac{\pi}{2} - \theta \bigg) = \sin\theta \\ \lambda_{21} & = & \cos(x'_2,x_1) & = & \cos \bigg( \frac{\pi}{2} + \theta \bigg) = - \sin\theta \\ \lambda_{22} & = & \cos(x'_2,x_2) & = & \cos\theta \end{array} \right\}$$\left. \begin{array}{lllll} \lambda_{11} & = & \cos(x'_1,x_1) & = & \cos\theta \\ \lambda_{12} & = & \cos(x'_1,x_2) & = & \cos \bigg( \frac{\pi}{2} - \theta \bigg) = \sin\theta \\ \lambda_{21} & = & \cos(x'_2,x_1) & = & \cos \bigg( \frac{\pi}{2} + \theta \bigg) = - \sin\theta \\ \lambda_{22} & = & \cos(x'_2,x_2) & = & \cos\theta \end{array} \right\}$

## Example 2.

### code

$$\begin{array}{rcl} \vec{A} \cdot \vec{r} & = & A_1 x_1 + A_2 x_2 + A_3 x_3 \\ & = & A^2 \\ & = & A^2_1 + A^2_2 + A^2_3 \end{array}$$

### Result

$\begin{array}{rcl} \vec{A} \cdot \vec{r} & = & A_1 x_1 + A_2 x_2 + A_3 x_3 \\ & = & A^2 \\ & = & A^2_1 + A^2_2 + A^2_3 \end{array}$$\begin{array}{rcl} \vec{A} \cdot \vec{r} & = & A_1 x_1 + A_2 x_2 + A_3 x_3 \\ & = & A^2 \\ & = & A^2_1 + A^2_2 + A^2_3 \end{array}$

## References

http://study-astrophysics.com/marion-01-08/