In the 2nd Quadrant, SINE is the only Positive. Where \theta is 30 for the first quadrant and 150 in the 2nd quadrant, which makes COSINE negative Sin \theta = \(\frac{1}{2}\) \theta = Sin\(^{-1}(\frac{1}{2}\)) = 30º which is positive in the first quadrant Sin 30 = Sin 150, i.e, (180 - 30), which is also positive in the second quadrant. BUT Cos \theta = -\(\frac{\sqrt{3}}{2}\) \theta = Cos\(^{-1}\)(-\(\frac{\sqrt{3}}{2}\)) = 150º which is in the second quadrant but negative Hence, \theta = 150º