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Darion

Can someone help me please? Rewrite with only sin x and cos x. cos 2x + sin x

  • one year ago
  • one year ago

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  1. Schrodinger
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    Okay. So this stems from trigonometric identities and double angle formulas. Do you know any double angle formulas?

    • one year ago
  2. Darion
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    Not really, no. Sorry

    • one year ago
  3. Schrodinger
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    No prolem. A really good reference for all of these formulas would be this: (one minute.)

    • one year ago
  4. Schrodinger
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    *No problem. Anyways, here's the webpage with pretty much every possible identity you can imagine for Trig. http://www.sosmath.com/trig/Trig5/trig5/trig5.html You'll notice that under the double angle formulas section, Cos(2x) has three different accompanying equations. Can I ask what math you're in right now, i'm assuming Precalc?

    • one year ago
  5. Darion
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    You are correct, I'm in precalc. And thanks for the link btw. That is awesome.

    • one year ago
  6. Schrodinger
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    \[\cos(2x) = \cos ^{2}(x) - \sin ^{2}(x)\]\[\cos(2x) = 2\cos ^{2}(x)-1\]\[\cos(2x) = 1 - 2\sin ^{2}(x)\]

    • one year ago
  7. Schrodinger
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    No problem. Okay, given these formulas, we can substitute cos(2x) for other things without double angles. Right now, we've got \[\cos(2x) + \sin(x)\], correct?

    • one year ago
  8. Darion
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    Yes

    • one year ago
  9. Schrodinger
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    (Sorry for asking something you obviously know the answer to, just giving myself time to think LOL. I haven't done this in a while.)

    • one year ago
  10. Darion
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    No you're doing great. You're helping me way more than anyone has thus far. Take all the time you need I really appreciate your helping me out man.

    • one year ago
  11. Schrodinger
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    No worries. I'm a little confused about the vague instructions. While you can rewrite it with those terms, i'm wondering if it's acceptable to have only sine, only cosine, or whether cosine or sine squared is acceptable. After all, that is basically what these are. Guess every case might be worked out.

    • one year ago
  12. Darion
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    If it helps, the possible answers are: 1 + 3 sin x 1 + 3 sin2x 1 - 2 sin2x + sin x 1 + 2 sin2x + sin x

    • one year ago
  13. Darion
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    The last 3 are (sin^2 x) btw

    • one year ago
  14. Schrodinger
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    Oh, lol, okay then. That's WAY simpler than what I was about to do. My bad, I was like, half-trying to solve a trig identity. So yeah, just take a look at the formulas I put up, and substitute them. From there it's super easy to see which one makes sense with the possible answers.

    • one year ago
  15. Schrodinger
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    Don't try to solve anything, just see which substitution would get you closest to the answers given. It should be a single step.

    • one year ago
  16. Schrodinger
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    You follow?

    • one year ago
  17. Darion
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    I think so. So the answer would just be 1 - 2 sin2x + sin x

    • one year ago
  18. Schrodinger
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    Exactly, but I have to say, don't be afraid of using the carat symbol (^) if you're ever writing something on a computer and can't put in a fancy superscript like: \[\sin ^{2}x\] to denote when a value is squared. People could very, very easily misread it as sin(2x) instead of sin^2(x), and that could mess up a whole problem.

    • one year ago
  19. Darion
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    Thanks for the tip and all your help. I can't thank you enough.

    • one year ago
  20. Schrodinger
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    No problem. Good luck with Precalc. I struggled a lot with it when I first learned it.

    • one year ago
  21. Schrodinger
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    (Heck, i'm still learning it, albeit different forms.)

    • one year ago
  22. Darion
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    Haha. I guess it never really ends does it?

    • one year ago
  23. Schrodinger
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    Nope. We're dumb forever. :P PS, I don't know if this would apply to you, but do you use flash cards to study?

    • one year ago
  24. Darion
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    sometimes. I guess it depends on what I am studying. If there are a lot of vocabulary words or something I will usually use flashcards.

    • one year ago
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