#### Answer

the identity cot α = $\frac{cos α}{sin α}$ is valid

#### Work Step by Step

cot α = $\frac{b}{a}$
cos α = $\frac{b}{c}$ ; sin α = $\frac{a}{c}$
$\frac{cos α}{sin α}$ = $\frac{\frac{b}{c}}{\frac{a}{c}}$= $\frac{b}{a}$
So cot α and $\frac{cos α}{sin α}$ are equivalent