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Math Help - work out missing angle?

  1. #16
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    -100 on each side, -121 on each side and +220 on each side so yo end up with 323=cos(?)
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  2. #17
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    Too many steps at once. Try the -100 and -121 first. What equation do you get then?
    Last edited by Ackbeet; December 15th 2010 at 08:35 AM. Reason: Grammar.
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  3. #18
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    103=-220cos(?)
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  4. #19
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    Correct. Now what is the -220 doing to the cosine?
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  5. #20
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    im not too sure what it is doing
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  6. #21
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    would you +220to (?) so it looks like 103=cos(220)?
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  7. #22
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    No, no. It's multiplying the cosine. You have -220 times the cos(?). You would like to get rid of the -220, because it's preventing you from getting the cos(?) all on one side, with everything else on the other. So, how do you "reverse" multiplication?
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  8. #23
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    times -220 by cos(?) ??
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  9. #24
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    No, that's what you already have. Here's an analogy: solve 4 = 6x for x. What do you do?
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  10. #25
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    4/6=0.6
    for my one i would do, 103/-220= 0.47?
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  11. #26
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    Well, in the first case, you would probably write 0.67 instead of 0.6, but you have the right idea. Incidentally, because you are dividing a positive by a negative, the final result should be what: positive or negative?
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  12. #27
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    nagative?
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  13. #28
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    Correct. So your equation is now what?
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  14. #29
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    18^2= 10^2+11^2-2x10x11xcos?

    324=100+121-220cos?

    103=-220cos?

    103/-220= -0.47

    ?=-0.47???
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  15. #30
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    No. You have

    cos(?) = -0.47.

    Now you want to find the ?, but it's inside the argument of the cosine function. So how do you "undo" a cosine function?
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