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Hi,Thank you for using JustAnswer.The half-angle identity for cosine is:cos(a/2) = ±√(1 + cos a)/2Using this:cos(pi/12) = cos (pi/6 / 2) = ±√(1 + cos pi/6)/2 = ±√(1 + √3/2)/2 = ±√(1/2 + √3/4)cos(pi/12) = ±√(2+√3) / √4cos(pi/12) = ±(1/2)√(2+√3)cos(pi/12) ≈ 0.9659Please let me know if you need to match a specific answer choice like some of yesterday's problems.Thanks.
Hi,That depends on if they are asking for a value or an expression.If they want a value, then it is 0.9659, when rounded to four decimal places.If they want an expression, then it could be ±√((1 + cos pi/6) / 2). In this case though, it would be helpful to see the answer choices that are available (if it is multiple choice).Thanks.
Hi,The answer for cos(pi/12) happens to be the same as the answer for sin(7pi/12).It looks like this:(The computer program might not care about the ± sign though...)Thanks.