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anonymous

  • one year ago

help please :)Students are building a trebuchet for their physics class. The model is shown below. If the length of DA measures 25 inches, then what to the nearest inch is the measure of the support AC?

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  1. anonymous
    • one year ago
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  2. zepdrix
    • one year ago
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    |dw:1441847743206:dw|

  3. zepdrix
    • one year ago
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    So just some trig stuff, ya? :)

  4. anonymous
    • one year ago
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    okay how would I figure this out?

  5. zepdrix
    • one year ago
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    In relation to our angle, we care about the side `adjacent` (next to it), and the side `opposite` the angle as well.

  6. zepdrix
    • one year ago
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    Which of your three trig functions makes use of `adjacent` and `opposite`? :)

  7. anonymous
    • one year ago
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    sine cosine tangent?

  8. zepdrix
    • one year ago
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    Yes, those three are the ones we're considering.\[\rm \sin \theta=\frac{opposite}{hypotenuse},\qquad \cos \theta=\frac{adjacent}{hypotenuse},\qquad \tan \theta=\frac{opposite}{adjacent}\]It looks like tangent is the one we want, ya? :D

  9. anonymous
    • one year ago
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    yes

  10. zepdrix
    • one year ago
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    \[\large\rm \tan\theta=\frac{opposite}{adjacent}\]So we need to plug in the angle and side lengths.\[\large\rm \tan55^o=\frac{x}{25}\]Understand how I was able to set that up? :o

  11. anonymous
    • one year ago
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    not really

  12. zepdrix
    • one year ago
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    |dw:1441848312912:dw|If our angle is located here in the upper left corner, then our side opposite the angle is over here.

  13. anonymous
    • one year ago
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    okay yea I do sorry that was so obvious lol

  14. zepdrix
    • one year ago
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    The side we're trying to solve for, I labeled x. So we need to isolate the x. It's being divided by 25. How can we undo that?

  15. anonymous
    • one year ago
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    Do we divide it by 3?

  16. zepdrix
    • one year ago
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    Sorry it didn't give me the notification D: We're dividing by 25, so let's multiply both sides by 25 to undo that :D

  17. zepdrix
    • one year ago
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    \[\large\rm 25\cdot\tan55^o=\frac{x}{\cancel{25}}\cdot\cancel{25}\]

  18. anonymous
    • one year ago
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    so I need to multiply 25*55?

  19. zepdrix
    • one year ago
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    No! Be careful not to do that! :) Maybe I should have put brackets around our 55 to be clear. He is the argument of your trig function, he is trapped inside of there. He can't come outside, and the 25 can't come inside. He's grounded :O

  20. zepdrix
    • one year ago
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    \[\large\rm 25\cdot\color{orangered}{\tan(55)}=x\]

  21. zepdrix
    • one year ago
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    You can probably put it into your calculator all at once like that! :) \(\large\rm 25\times\tan(55)\) Make sure you're in `degree mode`!

  22. anonymous
    • one year ago
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    35?

  23. zepdrix
    • one year ago
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    Yay good job \c:/

  24. zepdrix
    • one year ago
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    Rounded closer to 36 I guess :) But whatever

  25. anonymous
    • one year ago
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    it wasn't an option but thank you I really didn't understand this but thank you so much for walking me through it. :)

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