Just to confirm, are you using the double angle relationship (cos(2x) in terms of cos(x)) to answer your question?
Given cosθ=-3/5 and π < θ < 3π/2, use an appropriate trigonometric identity to evaluate exactly.
1) cos θ/2
I got :
√(1+cosθ/2) = √(1+(-3/5)/2) = √((2/5)/2) = √(5)/5
I realize that they are referring to quadrant 3, I'm not really sure why that is relevant in the question. Could someone please explain that to me? And also if I have the right answer?
Thank you very much!