## Precalculus (6th Edition) Blitzer

If $\theta$ lies in quadrant III, tangent and cotangent are positive.
The values of all the trigonometric ratios are positive in quadrant I. Sine and cosecant are positive in quadrant II and the remaining functions are negative. Tangent and cotangent are positive in quadrant III and the remaining functions are negative. Cosine and secant are positive in quadrant IV and the remaining functions are negative. Thus, if $\theta$ lies in quadrant III, tangent and cotangent are positive.