i need to find (cosθ)\({^2}\) = 1 in the domain \({-360°≤θ <360°}\)
i know i can use the unit circle and quadrantal angles. however, i'm thrown off by the square because i've never encountered a problem like this before? how should i solve it?
for instance, (cos 180)\({^2}\) = -1 isn't possible. however, 180° is a possible answer?
the answers in the textbook are -360°, -180°, 0°, and 180°.