## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\text{Quadrant IV}$
$P= (x,y) \text{ is the point on the unit circle corresponding to } \theta$ We have: $\cos{\theta} = x>0$ $\tan{\theta} = \dfrac{y}{x} <0$ With $x\gt 0 \text{ and } \tan{\theta}\lt 0$, then $y<0$ Note that points in Quadrant IV have $y\lt 0 \text{ and } x\gt 0$ Thus, $\theta \in \text{Quadrant IV}$