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Math Help - Trigonometry - Half angle??

  1. #1
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    Trigonometry - Half angle??

    cos(5[pi]/24)+cos([pi]/24)

    i have to find the exact value of that.

    so I simplified cos(5pi/24) to cos(pi/3 - pi/8) and then used a difference formula for cos to get
    (sqrt2/2){[sqrt2+(sqrt2)]} + (sqrt3/2){[sqrt2-(sqrt2)]}

    did the same thing for cos(pi/24) and got
    (sqrt3/2){[sqrt2+(sqrt2)]} + (1/2){[sqrt2+(sqrt2)]}

    so where do i go from there? How do I add these huge squarerooted expressions together to find the exact value? Please help. I'm running out of time and getting frustrated! Thank you!
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  2. #2
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    anyone see what im doing wrong, if anything?


    also... this homework assignment says to simplify without calculators:

    Cos(85deg)sin(40deg)+sin(-5deg)sin(-50deg) - how do i go about doing that? do you think it is a typo where the sin(40deg) should be cos? cause that would make a lot more sense to me.
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