Rotating a point around the origin

Point $\blue{P}$ is at $(1,0)$. Point $\blue{P}$ is rotated by $\theta$ *counter-clockwise* about the origin, to point $\green{P'}$.  **What are the coordinates of $\green{P'}$ in terms of $\theta$ ?** $P'_x = $ [[☃ expression 1]] $P'_y = $ [[☃ expression 2]]