solving for x with cosine

To be honest, it's been so long since I worked with trig functions, I'm not even sure if I start with a unit circle or the inverse of cos
 
First solve the equation for cos(x) which has nothing to do with trigonometry. Maybe it would be helpful if when you look at the equation wherever you see cos(x) you see (big) X and then solve for X. Then we can talk about unit circles, etc.
 
I got approximately 11. 74 solving just for x, however the problem I was solving requests the answer in degrees, and I believe the answer is supposed to be in the second quadrant, so that doesn't line up to me
 
Can we see how you got the answer for x=11.74 so we can show you how to adjust your x= 11.74, if that is correct.

There are different ways to solve this problem so if we see your work we can continue from there.
 
Well, I added one to both sides (2cos(x)= -0.2814) , divided both sides by two (cos(x)= -0.2814/2), then I found the inverse cos of both sides (x= (cos^-1)(-0.2814/2).
 
weebangie said:
Well, I added one to both sides (2cos(x)= -0.2814) , divided both sides by two (cos(x)= -0.2814/2), then I found the inverse cos of both sides (x= (cos^-1)(-0.2814/2).
Click to expand...
If you are allowed to - use a calculator to calculate 'x'.
 
I did, that's where I got x = 11. 74, I just don't feel like that would be the correct answer to a question expecting a degree in the second quadrant. Which makes me think that I'm not supposed to just solve for x, but rather use either the unit circle or the reciprocal of cos.
 
weebangie said:
Well, I added one to both sides (2cos(x)= -0.2814) , divided both sides by two (cos(x)= -0.2814/2), then I found the inverse cos of both sides (x= (cos^-1)(-0.2814/2).
Click to expand...
When I do that, which is the right thing to do, I get 98.088354 degrees. I can't see how you would get 11.74.

Can you tell us exactly what buttons you pressed, in what order, and what model of calculator you have? That will help a lot.
 
weebangie said:
Well, I added one to both sides (2cos(x)= -0.2814) , divided both sides by two (cos(x)= -0.2814/2), then I found the inverse cos of both sides (x= (cos^-1)(-0.2814/2).
Click to expand...
You were asked how you got 11.74! "cos^(-1)(-0.2814)" is NOT 11.74 whether you are in "degrees", "radians", or "grads".
In degrees, cos^(-1)(-0.2814)= 98 degrees which IS in the second quadrant.
 
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