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

Algebra ->  Trigonometry-basics -> 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      Log On

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

 

Then 

 

And 

, 

, 

Substitute for 11 and  in












 
Edwin