2 theta is in what quadrant?

Question

whpalmer4 · Answer

That depends on the value of $\theta$, of course...

anonymous · Answer

the problem does not tell me the value. What i asked is what I was asked :o

whpalmer4 · Answer

There must be other context.  Otherwise, the question is equivalent to asking is $x>3$ without any other information.

anonymous · Answer

woops. i was suppost to use 
Use the equation 8x 2 - 4xy + 5y 2 = 36 to find tan 2theta.  
(which is -4/3)


 could you help me answer it now?

whpalmer4 · Answer

So $$\tan\,2\theta = -\frac{4}{3}$$and we are to determine which quadrant contains $2\theta$?

anonymous · Answer

yes

whpalmer4 · Answer

Is that going to be a positive value of $\theta$ or a negative one?

anonymous · Answer

The options are quadrant 1, 2, or 4. I found theta (-26.56)     so am i correct in saying its quadrant 4?   i used theta= 1/2 tan^-1 (-4/3
)

whpalmer4 · Answer

Well, I think quadrant IV is the right answer, but I'm not quite sure I see how you got $\theta = -26.56$

anonymous · Answer

I used tan 2 theta= B/ A-C     i found that B/(A-C) is (-4/3) from the original equation. 
Then used theta = 1/2tan^-1 B/(A-C)

whpalmer4 · Answer

Yes, I understand the formula you used, but I don't see how you get -26.56 as an answer.  When I take the arctan of -4/3, I get -0.927295 radians.

anonymous · Answer

hmm.. i was using degrees and i probably messed up.  (im using an iphone app)
 but i just replugged it in and got the same thing.  so quadrant 4 is the right answer?

anonymous · Answer

Im probably going to ask more questions in this section