If Sin X = -4/5 and X is in Quadrant 4, then find Cos 2X
I have used the Double Angle ID and I got -7/25 as my answer.
However, here is where my problem is at. The question says that X is in Q4, so therefore Cos has to be positive right?
This was a question that I did on my Trig test and I got it wrong...the choices were...
I chose D because Cos is positive in Q4, however the correct answer was B, the exact same answer I got when I used the double angle formula...but it says X is in Q4????
Can somebody explain this to me please? Thanks!
omg someone please answer me