Question 1194583
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With 0 < a < b, the figure below shows two angles α and β drawn in the unit circle 
so that sin(α) = a and sin(β) = -b. Express sin(α + β) in terms of a and b.
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As it is posted in your message, &nbsp;the problem's formulation is &nbsp;INCOMPLETE.


To be complete, &nbsp;the wording formulation &nbsp;MUST &nbsp;SAY &nbsp;EXPLICITLY, &nbsp;in which of four quadrants
each of the angles  " α "  and  " β " is located.



It is a necessary condition for the problem to be formulated properly: 
without it, &nbsp;the problem &nbsp;CAN &nbsp;NOT &nbsp;be solved correctly.