Question 728187
show that cos(A-B)-cos(A-B)=2 sinA sin B.
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"show that..." implies you want to confirm an identity.
But, cos(A-B)-cos(A-B) = 0
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Using coumpand angle and indenty for cos.
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Then you say, "solve that question?"
Questions are answered.
Equations are solved.
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Try again.  Make it clear what you want to do.