Question 931504
Evaluate sin(v − w) if tan v = 3/4 v is in Quadrant III, sin w = − √(10)/10 and w is in Quadrant IV. 
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sinv=-3/5 (working with (3-4-5) reference right triangle in quadrant III where sin<0, cos<0.
cosv=-4/5
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sinw=-&#8730;10/10
cosw=&#8730;(1-sin^2(w))=&#8730;(1-(1/&#8730;10)^2)=&#8730;(1-(1/10))=&#8730;(9/10)=3/&#8730;10=3&#8730;10/10
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sin(v-w)=sinv*cosw-cosv*sinw=-3/5*3&#8730;10/10-(-4/5)*(-&#8730;10/10)
=-9&#8730;10/50-4&#8730;10/50=-13&#8730;10/50