- #1

#### Quanta

How author derives these old basis unit vectors in terms of new basis vectors ? Please don't explain in two words.

[itex] \hat{e}_x = cos(\varphi)\hat{e}'_x - sin(\varphi)\hat{e}'_y[/itex]

[itex] \hat{e}_y = sin(\varphi)\hat{e}'_x + cos(\varphi)\hat{e}'_y[/itex]

[itex] \hat{e}_y = sin(\varphi)\hat{e}'_x + cos(\varphi)\hat{e}'_y[/itex]