## Trigonometry 7th Edition

By Definition I- $\sin\theta$ =$\frac{y}{r}$ $\sin\theta$ is negative, hence y is negative as r being distance can not be negative. 'y' is negative in Quadrant III and IV. $\tan\theta$ =$\frac{y}{x}$ If y is negative, then $\tan\theta$ can be negative only when x is also negative. Therefore x and y both are negative i.e. terminal side lies in Quadrant III