Find sec(theta) if tan(theta)=sqrt(3)/3, and sin(theta)<0.
tan is + and sin is < 0, that is - ; that is in the 3rd quadrant.
But in the 3rd quadrant only tan and cot are positive, the rest negative.
, from this we have,
sec = -(2/3)(sqrt 3)
the negative sign ( - ) is introduced since it is in the 3rd quadtant