## Trigonometry (10th Edition)

1. r is always positive, because of square root 2. Let's consider quadrants and sign of (x,y) coordinates $quadrant (x,y):$ $Quad I$ $(+,+)$ $Quad II$ $(-,+)$ $Quad III$ $(-,-)$ $Quad IV$ $(+,-)$ 3.In Q1 x is positive , so $\frac{x}{r}$ is positive