How do you find the exact value of #cos ((-2 pi) / 3)#?

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Answer 1 · 2018-07-03T09:16:25

#color(purple)(=> -1 / 2#

#cos -theta = cos theta#

#:. cos (-(2pi)/3) = cos ((2pi)/3)#

#cos ((2pi)/3) = cos (pi - (pi/3) = -cos (pi/3) = -1 / 2#

Answer 2 · 2018-07-03T09:25:56

#-1/2#

#cos(-(2pi)/3)=-cos(pi/3)=-1/2#