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Pre-calc Proofs

Mr. EricMr. Eric
edited September 2008 in Everything Else
I don't need reasons, just the steps.

Cos2x=(1-tan^2x/1+tan^2x)

Comments

  • lackofcheeselackofcheese
    edited September 2008
    Here, have it in LaTeX ;)
    If you can't get it to a format you can read, your loss :D
    Also, I've taken the double-angle identity for granted; I'd hope you'd remember that one by now.

    \begin{align*}
    \frac{1-\tan^2x}{1+\tan^2x} &= \frac{1-\sin^2x/\cos^2x}{1+\sin^2x/\cos^2x} \\
    &= \frac{\cos^2x-\sin^2x}{\cos^2x+\sin^2x} \\
    &= \cos^2x-\sin^2x \\
    &= \cos2x \\
    \end{align*}
    Post edited by lackofcheese on
  • ......
    No. How do you think you will learn if you ask others to make your homework?
  • lackofcheeselackofcheese
    Whether or not he learns isn't really our problem. More to the point, it's not something we can enforce. If I hadn't told him, he'd google for the answer and find it in no time at all.
    At least this way he'll learn some LaTeX I hope.
  • Mr. EricMr. Eric
    That answer was so helpful =p. And don't worry, I've spent at least 30 minutes on this. I've tried to learn. Thanks though, I go learn latex to do this.
  • kiwi_birdkiwi_bird
    Whether or not he learns isn't really our problem.
    You once had a very different opinion.
  • lackofcheeselackofcheese
    edited September 2008
    Heh; I probably did, but cynicism creeps in oh so quickly.
    It would probably be funny if you had a specific post of mine to show me.

    Also, I guess it depends on one's mood at the time.
    Post edited by lackofcheese on
  • kiwi_birdkiwi_bird
    I've made some Excel that works for one problem; it was pretty easy but I can't be bothered making it do 10 at once / sequentially. However, of course, I won't give it to you.
    Link

    Though looking back you really did try to help. I was just to thick-headed to get it.. ^^ The sad think is the job I had to do this for was happy with a much easier solution.
  • Mr. EricMr. Eric
    Well I figured it out before I learned LaTex, but thanks.
  • lackofcheeselackofcheese
    In that case, I'll tell you the simplest thing you could have done was to paste my LaTeX into this website:
    CodeCogs LaTex Equation Editor

    LaTeX is cool, and far more portable than any other equation format.
  • Mr. EricMr. Eric
    Holy shit I just mindgasmed. I need to show this to all of my math teachers who write in the exponents and square roots.
  • kiwi_birdkiwi_bird
    I've been forcing myself to use LaTeX for all my school work and I've been learning a lot.
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