Question 34075
You want 2sin(theta) + 1 = 0.  So, we know that we need 2sin(theta) to add up to be negative 1 so that when we add one we get zero.  We also know that we need sin(theta) to be -1/2.  Working out the equation, if sin(theta) is -1/2 then when multiplied by two and added to one, we get zero. 

Now, we need to find which values of theta give sin(theta)=-1/2 This occurs at 210 and 330 degrees (when the Hypotenuse is negative on the coordinate plane).