The problem is to find Tan(B / 2)

What is the cosine of Tan(B) when (pi/2 < B < pi) which would be quad 2.

tanB = (sqrt(11) / 5)

Seems to me that since tan = sine / cosine, the cosine would be 5, but Coursecompass.com (the site where I do all my homework) insists this is incorrect.

TIA

- Rusty