# Geometry - Rotation

## 1 - About

Rotation is a geometric transformation and can be applied through the following transformation matrix

## 3 - Rotation by

### 3.1 - 90 degrees

$M = \begin{bmatrix} 0 & -1 \\ 1 & 0 \end{bmatrix}$

### 3.2 - $\theta$ radians

$M = \begin{bmatrix} cos(\theta) & -sin(\theta) \\ sin(\theta) & cos(\theta) \end{bmatrix}$

180 degrees = $\pi$ radians

Identity: $sin^2(\theta) + cos^2(\theta) = 1 \text{ for all } \theta$