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March 28, 2017

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sin(-15)
tan(165)

  • advanced math - ,

    I bet it said "find the exact value"

    sin(-15) = sin(30-45)
    = sin30cos45 - cos30sin45
    = (1/2)(√2/2) - (√3/2)(√2/2) = (√2 - √6)/4

    tan(165) = tan(120+45)

    = (tan120 + tan45)/(1-tan120tan45)

    tan 120 = -tan60 = -√3

    so back into the above result
    = (-√3 + 1)/(1 - (-√3)(1)) = (1-√3)/(1+√3)

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