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anonymous
 one year ago
Find an exact value. cos(pi/12)
anonymous
 one year ago
Find an exact value. cos(pi/12)

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welshfella
 one year ago
Best ResponseYou've already chosen the best response.1i think we can use cos 2x = 2cos^2x  1 cos (pi/6) = 2 cos^ (pi/12)  1 cos pi/6 = sqrt3/2

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0they want you to use the half angle formula \[\cos \frac{ x }{ 2 }= \pm \sqrt{\frac{ 1+cosx }{ 2 }}\]

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1oh ok well just plug cos x ( in this case cos pi/6) into the firmula and work it out

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0when I do I don't get the right answer

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0The answer options are (sqrt6+sqrt2)/4 (sqrt6+sqrt2)/4 (sqrt6sqrt2)/4 (sqrt6sqrt2)/4

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1yes its an awkward one to work out

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0How would you work it out?

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1= sqrt [( 1 + sqrt3/2)/ 2]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0How do you get from that to one of the answers? I dont understand how you get a sqrt 6 out of any of that

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1i simplified that to (1/2)( sqrt(2 + sqrt3))

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1i agree I think those answers are wrong.

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1because if you go on the calculator cos pi/12 = 0.9659 and my answers comes to the same value

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1oh hold on (sqrt6+sqrt2)/4 comes to 0.9659 as well so that one is right

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1 also the negative of that is another solution

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1I'm not sure how they got to that ...
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