SOLUTION: By expanding cos(x-60), express 7cos(X) + 8cos(x-60) in the form Rsin(x+y),where R>0 and y is acute. I expanded cos(x-60) using an identity and got cos(x)cos60+sin(x)sin60 but the

Question 1048799: By expanding cos(x-60), express 7cos(X) + 8cos(x-60) in the form Rsin(x+y),where R>0 and y is acute.
I expanded cos(x-60) using an identity and got cos(x)cos60+sin(x)sin60 but then couldn't understand how to express that in the form Rsin(x+y).
Answer by Edwin McCravy(20056) (Show Source): You can put this solution on YOUR website!











Draw a right triangle with opposite side 11 and adjacent
side , and angle y

 

Then 

 

And 

, 

, 

Substitute for 11 and  in












 
Edwin

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