Re: Trigonometric Identity

You've already shown:

What does each of these inequalities tell you about ?

Re: Trigonometric Identity

Too be honest I am not really sure >.<

that 2 theta is positive?

Re: Trigonometric Identity

It might help if you consider as a single variable. That is, let (a is for angle!) Now, each of the values you calculated is positive.

What quadrants can a be in to make sin(a) positive?

What quadrants can a be in to make cos(a) positive?

What quadrants can a be in to make tan(a) positive?

Re: Trigonometric Identity

oh I get it .. so Quadrant I. Because sin, cos and tan are all positive in Quadrant I