Question

Is arccos (sin (pi/6)) equal to pi/3 or 5pi/3?

Answer 1

I'm quite confused. With a look at the unit circle, I hope you can understand why...

Answer 2

Usually, when we talk about arccos, we restrict the range to [0, pi]. Of course, there are other angles that will give that value of cos, but in the interest of having a single-valued function, the range is usually restricted.

Answer 3

Oh, I thought it was restricted to the first and fourth quadrants...

Answer 4

That would be for arcsin. Note that if you go in quadrants I and IV for cosine, you get more than one answer. For sin, there is only one value.