SOLUTION: 2 sine theta + 1 = 0, 0 is less than or equal to theta which is less than 2 pi

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2 sine theta + 1 = 0, 0 is less than or equal to theta which is less than 2 pi
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2*sin + 1 = 0
2*sin = -1
sin = -1/2
Theta = 150 degs, or -30 degs, n*(-360) - 30 degs.
-390 is less than 360 (2 PI), but it's probably not the answer wanted.
150 is probably the one expected. The limits are loosely specified.