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Inverse trigonometric functions and reference angles?
So I have this problem written in my notes and I have no idea why the answer is what it is. The problem is the inverse cos of 1/3 equals what.
So I plug that in my calculator and get 70.5 degrees, but my notes say that that is the reference angle and the actual answer is 289.5 degrees, which I believe is 360-70.5. I need help because I don't understand this! Any help is appreciated!
1 Answer
- 8 years agoFavorite Answer
Both answers can be considered. The cosine value is positive (we're dealing with a positive value which is 1/3) when the angle is at quadrants 1 and 4. Thus, for this problem, there may be 2 answers. One is 70.5 degrees. Then, the other can be solved by using 70.5 as reference. It can actually be -70.5 degrees. But, since its easier to deal with positive angles, we compute for its corresponding positive angle. 360-70.5 = 289.5 degrees which is the other answer.
