Solve for θ in the equation cos θ = 0.778 when 180º < θ < 360º. Round your answer to the nearest tenth of a degree.

Answer 1

180º < θ < 360º and cosθ is positive means that θ lies in quadrant IV

On your calculator enter:
2ndF
cos
.778
=
and you should get and acute angle.
that would be the angle in standard position, so
θ = 360- angle = ..... to the nearest tenth.

check by taking cos(of your angle)

let me know what you get.

Answer 2

I get 38.9 and then subtracting it from 360 gets 321.1 which isn't the correct answer, apparently.

Answer 3

That is the answer I got,

and when I find cos 321.1 , I get .778243, which matches the given
considering that we rounded to one decimal.

Our answer is correct.

Answer 4

Well, I've tried every possible variation for it, but it won't say it's correct. I'll ask my teacher. Thank you so much!

Answer 5

just a thought ... are you using the degree symbol in your answer?

321.1º

alt-167

radians is the default I think ... degrees must be specified

Answer 6

The domain was definitely given in degrees:
180º < θ < 360º