tan(-120)= sqrt 3 OR - sqrt 3
(Helper stated that it was sqrt 3)
But, I'm just confused over this part:
for even vs. odd functions it saids that tan(-angle) = - tan(angle)
so the even vs. odd doesn't matter since tan is positive in the QIII?
Tangent is an odd function. As you correctly mentioned, a test for an odd function is
if f(-x)=-f(x) for all x in the domain, then f(x) is an odd function.
Tangent fits into this category.
Since tan(120°)=-√3, tan(-120°)=√3, as Helper pointed out.
Do not forget that tan(x) has a vertical asymptote at π/2, 3π/2, ... with a period of π, while sin(x) and cos(x) have a period of 2%pi;.
Also, in case you do not already know,
an even function f(x) is such that for all x, f(x)=f(-x), example: x²=(-x)².