 In this video we provide the solution to question number seven for practice exam number three for math 1060 We need to find all solutions to the equation to cosine of theta equals one So if we solve for the trigonometric function, we're gonna cosine theta is equal to one half So we have to think about in the unit circle because we don't have a calculator here We can't just compute our cosine. We have to think about in the unit circle when is cosine equal to one half Cosine is going to go to one half. This will happen the first quadrant and in the second quadrant if we think of our picture right here, right? Here's the unit circle one half x equals one half would be something like that first quadrant the second quadrant So in the first quadrant this happens thinking of radian measure, right? This happens at pi thirds Right, but this will also happen for any multiple that of 2 pi we add to that so we get 2 pi k So we can already eliminate some of the answers based upon that already But in the fourth quadrant we have to remember that one the angle that references 2 pi thirds in the fourth quadrant will be 2 pi Take away pi thirds So that's gonna be 5 pi thirds But they have to add any multiple 2 pi to that as well because the answers do repeat themselves with a 2 pi period So looking for looking for pi thirds and 5 pi thirds plus 2 pi k which all of them have that We see the correct answer would be choice F