SOLUTION: Express the function f(x)=5cos(2x)°-3sin(2x)° in the form f(x)=kcos(2x-α)°, where k>0 and 0≤α≤360

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Question 401136: Express the function f(x)=5cos(2x)°-3sin(2x)° in the form f(x)=kcos(2x-α)°,
where k>0 and 0≤α≤360
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!

Let cos%28alpha%29+=+5%2Fsqrt%2834%29 and sin%28alpha%29+=+-3%2Fsqrt%2834%29, where
alpha+ is in the 4th quadrant.
Then
5cos+%282x%29+-+3sin%282x%29+=+sqrt%2834%29%2Acos%282x+-+alpha%29