SOLUTION: whats the exact value of cos 15

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Question 730412: whats the exact value of cos 15
Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!
15° is the difference between the two special angles 45° and 30°

We use the formula

cos(A-B) = cos(A)cos(B) + sin(A)sin(B)

where A = 45° and B = 30°  

cos(15°) = 

cos(45°-30°) = cos(45°)cos(30°) + sin(45°)sin(30°) = 

 +  = 

 +  = 



Edwin
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