In triangle ABC, find sin A if b = 2*sqrt(10), c = 11, and a = 9.
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a2=b2+c2−2bc cosAcosA=b2+c2−a22bc=4⋅10+112−922⋅11⋅2⋅√10=8044⋅√10=2011⋅√10
sinA=√1−cos2A=√1−400121⋅10=√81121sinA=911=0.¯18
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