What is the value of Cos(15)?

Question: What is the value of Cos(15)? Solution : We shall write \[15^0=45^0-30^0 \] And apply Cos(A-B) formula \[Cos(A-B) =Cos(A)Cos(B)+Sin(A)Sin(B)\] Therefore \[Cos(15^0) = Cos(45^0-30^0) =Cos(45^0)Cos(30^0)+Sin(45^0)Sin(30^0) \] Now we shall substitute following values into above formulas \[Cos(45^0) =1/√2 , Cos(30^0) =…

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