Question

What is the exact value of `cot 210`?

Answer 1

On the trig unit circle:

`sin 210 = sin (30 + 180) = -sin 30 = -1/2`
`cos 210 = cos (30 + 180) = -cos 30 = (-sqrt3)/2`

`cot 210 = cos 210/sin 210 = [(-sqrt3)/2]:(-1/2) = sqrt3`