## Trigonometry (10th Edition)

$\sin180^{\circ}=\frac{y}{r}=\frac{0}{1}=0$ $\cos180^{\circ}=\frac{x}{r}=\frac{-1}{1}=-1$ $\csc180^{\circ}=\frac{r}{y}=\frac{1}{0}=undefined$ $\sec180^{\circ}=\frac{r}{x}=\frac{1}{-1}= -1$ $\tan180^{\circ}=\frac{y}{x}=\frac{0}{-1}=0$ $\cot180^{\circ}=\frac{x}{y}=\frac{-1}{0}=undefined$
The angle 180 degrees with (x,y) coordinates (-1; 0) $r=\sqrt {x^{2}+y^{2}}=\sqrt {(-1)^{2}+(0)^{2}}=\sqrt {1}=1$