### Home > PC3 > Chapter 9 > Lesson 9.2.1 > Problem9-102

9-102.

​Write the matrix associated with counterclockwise rotation through each of the given angle measures. Homework Help ✎

Think about the points $(1, 0)$ and $(0, 1)$. If you rotated them through the given angle, where would they end up?

1. $90º$

$(1, 0) → (0, 1)$
$(0, 1) → (−1, 0)$

$\begin{bmatrix}a&b\\c&d\end{bmatrix}\begin{bmatrix}1&0\\0&1\end{bmatrix}=\begin{bmatrix}0&1\\-1&0\end{bmatrix}$

1. $150º$

$(1, 0) \Rightarrow\left(-\frac{\sqrt{3}}{2},-\frac{1}{2}\right)$

$(1, 0) \Rightarrow\left(\frac{1}{2},-\frac{\sqrt{3}}{2}\right)$