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

The identity sec α = $\frac{1}{cos α}$ is valid
sec α = $\frac{c}{b}$ cos α = $\frac{b}{c}$ $\frac{1}{cos α}$ = $\frac{1}{\frac{b}{c}}$ = $\frac{c}{b}$ So sec α and $\frac{1}{cos α}$ are equivalent