My friend was supposed to help today during lunch but we got distracted by a game of Bullshit, so if anyone here can do this stuff, I'd really appreciate some help.

We're doing Law of Cos and here is a pic of the problem i have to solve:
picture 3 - hw help

I know I have to use the Side-Side-Side formula, which is: a^2-b^2-c^2 = -2bc(cosA)

Once everything is plugged in and switched around to isolate A, that formula turns into:
6^2 + 8^2 + 12^2 / 2(8)(12) = cosA

After that, to isolate A from cos, you need to use the inverse (divide both sides by cos) but I don't quite understand the whole inverse thing. I thought the inverse was when it was like cos^-1 but every time I plug that into my calculator, it says error and I don't know what I'm doing wrong.

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  • 3

    The answer is C.

    • ember
    • January 28, 2011, 9:09 am
    Nuh uh its 24!
    - Reddeath195 January 28, 2011, 9:23 am
    NO IT'S BLUE >:o
    - ember January 28, 2011, 9:25 am
    - Reddeath195 January 28, 2011, 9:32 am
    LIES!! IT'S OVER 9000!!
    - ember January 28, 2011, 9:37 am
    - Reddeath195 January 28, 2011, 9:42 am
  • 2

    ...What? @_@

  • 1

    Uhhhhhhhhhhhhhh......sorry. Wish I could help. +3 for taking an advanced math. I only took discrete math.

  • 1

    lol thanks. i figured it out...eventually....

  • 1

    is this cal. or trig

    It was Pre Calculus. But this is a really old post from the last school year. Sadly, I am now enduring the pain of AP Calculus x_x
    - ninjapoptart October 11, 2010, 6:07 pm
    yarg i hated calculus
    - triclebickle October 11, 2010, 6:17 pm
    Calculus can suck my non-existent balls. It makes absolutely no sense.
    - ninjapoptart October 11, 2010, 6:41 pm
    thats why i failed that class by doing jack shit and studying for classes that i needed
    - triclebickle October 11, 2010, 6:46 pm
  • 1

    why don't you use a calculator, rather than trying to do it 1940's way?

    I did try to use a calculator but I was plugging something in wrong and I wasn't sure what.
    - ninjapoptart October 11, 2010, 6:08 pm
  • 1

    I'm sorry to say this, but this is the easieast crap I've ever seen.

    epic bump is epic
    - Disco January 28, 2011, 6:29 am
  • 1

    Ok, so regular cosine, you use angles: cos(Angle)=number. Arccosine (or inverse cosine) uses numebrs: arccos(Number)=angle. There should be either an "arccos" or "cos^-1" button

  • 1

    a^2=b^2+c^2 -2bc*cos(A)
    36=64+144 -192*cos(A)
    36=208 -192*cos(A)
    192*cos(A) = 172

    Which makes sense, since when you visualize the triangle, angle A will be very small, so the cos will be a large number (but always less than 1).

    • Katt
    • January 28, 2011, 6:46 am
  • 1

    Oh yeah the answer is 26.4 degrees btw.
    (you f'd up the formula changing negatives to positives)

  • 1

    My head... It hurts.. Why?

    • SuDoku
    • January 28, 2011, 9:00 am
  • 1

    42 it's the answer to everything

  • 1

    this sounds so easy compared to calc 2. i miss precalc lol

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