SOLUTION: write the expression as sine, cosine or tangent of a single angle. cos(pi )/(6)cos(pi )/(7)-sin(pi )/(6)sin(pi )/(7)

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Question 1071448: write the expression as sine, cosine or tangent of a single angle.
cos(pi )/(6)cos(pi )/(7)-sin(pi )/(6)sin(pi )/(7)
Answer by ikleyn(52803)   (Show Source): You can put this solution on YOUR website!
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write the expression as sine, cosine or tangent of a single angle.
cos(pi )/(6)cos(pi )/(7)-sin(pi )/(6)sin(pi )/(7)
~~~~~~~~~~~~~~~~~~~` 

Apply the formula of sum for cosine:

cos(a)*cos(b) - sin(a)*sin(b) = cos(a+b).



    See the lesson   Addition and subtraction formulas  in this site.



You will get 

 =  =  = .

Solved.



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