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Find the exact value by using a half-angle identity. cos(5π/12) I know someone knows how to do this! if you could explain too, that'd be great!

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os 5π/12 cos ((5 pi/6)/2) = +/- sqrt( (1+cos (5 pi/6))/2 ) cos(5 pi/6) = -sqrt(3)/2 cos (5 pi/12) = +/- sqrt( (2/2-sqrt(3)/2)/2 ) cos (5 pi/12) = +/- sqrt( ((2-sqrt(3))/2)/2 ) cos (5 pi/12) = sqrt( ( (2-sqrt(3))/4 ) ) 5 pi/12 is in quadrant 1 so we choose the + sign because cos is positive there
thank you!!
your welcome

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Other answers:

wait did you like re-expand the problem after cos(5 pi/6) = -sqrt(3)/2
most of these problems are some identities written on the unit circle.
okay.. well can you please explain each of the steps this person just gave me? i would reaaaalllyyyy appreciate it
ok so 5pi/12 is 75 degrees rite
i guess.. lol is it?
pi is 180 you know that rite and u muliply tht by 5 and get 900 and divide 12 and you get 75 degrees
okay but what does the 75 degrees have to do with the formula?
just to make ur question simpler... for example lets say it asked u for the cos of pi/6 which is 30 degrees.
there is some thing called the unit circle and it has this angles from 30,45,60,90 upto 360.. and since we have cos of Pi/6 which is 30 degrees. we can look at the unit circle for the cosine of 30 degrees and find it
how is it done using half angle identity formula?!
ok so since they asked for cos(75) we can use the formula of using two angles to create that angle of 75. in this case we can use cos(45+35). u get tht?
so what in the world is the final answer? Is it cos(75)?

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