Solve Trig Question: cot(Arctan (-√(5)/2))

[majormuss]

Homework Statement

How do I solve this trig question?
cot(Arctan (-√(5)/2))

Homework Equations

The usual equation I know of which is easy o identify on the Unit circle is √3/2. I don't know how to approach this one..

The Attempt at a Solution

 

[HallsofIvy]

You do know that cot(x)= 1/tan(x) don't you? So cot(Arctan (-√(5)/2))= 1/tan(Arctan (-√(5)/2)).

And what do you think tan(Arctan (-√(5)/2)) is?