pre calc

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use an appropriate half-angle formula to find the exact value ofthe expression.
tan22.5

write the product as a sum
sinxsin5x

write the sum as a product
sin2x-sin7x

  • pre calc -

    sinxsin5x
    sinucosv= 1/2[cos(u-v)-cos(u+v)]

    = 1/2[cos(x-5x)-cos(x+5x)]

    = 1/2[cos(-4x)-cos(6x)]

    = 1/2cos4x-1/2cos6x

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