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The answers are $-\frac{5\pi }{24} ,-\frac{\pi }{24},\frac{19\pi }{24},\frac{23\pi }{24} $ But I don't know how you get $\frac{19\pi }{24},\frac{23\pi }{24} $ whenever I try and solve it I only get $-\frac{5\pi }{24} ,-\frac{\pi }{24}$.


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  • Where do we get the 2kπ from?

    • Mathe Mathe

      Cosine is periodic with period 2π. This means that cos(x) = cos( x + 2π ) = cos(x - 2π) = cos(x+4π) = cos(x-4π). So if x is a solution to cos(x) = sqrt(3)/2, x+2kπ will also be a solution,

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