Question

What is the cos(t) if t corresponds to the point (-2, 0)?

0
1
-1
Undefined

Answer 1

The cosine is the x-coordinate of the point on the unit circle at the angle of interest. It seems your point (-2, 0) corresponds to an angle of 180°. The ray through (-2, 0) from the origin intersects the unit circle at (-1, 0).
  cos(t) = -1