Is it ever possible that cos (A−B)=cos A−cos B? Why or why not?
Question
Answer:
Answer:The given equation is never possible i.e cos ( A - B ) ≠ cos A - cos B Step-by-step explanation:Given as :Is cos ( A - B ) = cos A - cos B To check this possibility , Let us put the value of angle A and B on both side of equation Now, Let A = 60° and B = 30° From Left hand side equation cos ( A - B ) = cos ( 60° - 30° )Or, cos ( A - B ) = cos 30°∴ cos ( A - B ) = [tex]\frac{\sqrt{3} }{2}[/tex]or, cos ( A - B ) = 0.866From Right hand side equation cos A - cos B = cos 60° - cos 30° Or, cos A - cos B = [tex]\frac{1}{2}[/tex] - [tex]\frac{\sqrt{3} }{2}[/tex]∴, cos A - cos B = 0.5 - 0.866I.e cos A - cos B = - 0.366 So, Left hand side ≠ Right hand sideSince while equating the values of angle A and b in the given equation on both sides, we get that the value of both sides are not equal , Thus we can say that the given equation is not equal to each other .Hence given equation is never possible i.e cos ( A - B ) ≠ cos A - cos B Answer
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