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It is given that sin(θ)=1/√15. In addition, a and b are coprime positive integers such that cos(2θ)=a/b. What is the value of a+b?

  • maths -

    cos 2Ø = 1 - 2sin^2 Ø
    = 1 - 2(1/15) = 1 - 2/15 = 13/15 = a/b
    and since a/b is in lowest terms
    a = 13, b=15

    so a+b = 28

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