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
