## Elementary Geometry for College Students (6th Edition)

The identity csc α = $\frac{1}{sin α}$ is valid
csc α = $\frac{c}{a}$ sin α = $\frac{a}{c}$ $\frac{1}{sin α}$ = $\frac{1}{\frac{a}{c}}$ = $\frac{c}{a}$ So csc α and $\frac{1}{sin α}$ are equivalent