Chapter 1 - Trigonometric Functions - Section 1.3 Trigonometric Functions - 1.3 Exercises - Page 26: 42

positive

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