Q:

1. If tanA=1/3 and pi<A<(3pi/2), calculate cos2A.

2. In what quadrant does the angle 2A lie?

A:

1. I don't need help with this one. Answer: cos2A=4/5 and lies in quadrant 3

2. I need help with this one. Can someone explain to me how I would know which quadrant the angle 2A would be in? How to approach and answer this?

Thanks!