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Question about simplifying this equation

  1. Mar 27, 2008 #1
    tan x/sin x + 1/cos x

    The choices are A. 2tan^2x B. 2cosx C. 2cosx-1 D. 2secx

    Do I make the tan sin/cos and multiply by reciprocal of sin? I did that and end up with 1/cos + 1/cos
     
  2. jcsd
  3. Mar 27, 2008 #2

    mathman

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    You got it right so far. Do you know what secx is?
     
  4. Mar 27, 2008 #3
    Tan x / Sin x + 1 /cos x

    Since tanx = (sinx/cosx) we can substitute and get:

    (Sinx / cos x)/ Sin x + 1 / cos x

    here we can cancel out the sin x 's and get

    1 / cos x + 1 / cos x

    since the denominators are the same we can add and get

    2 / cos x

    Now since sec x = 1 / cosx we get

    2 sec x


    Make sense?
     
  5. Mar 27, 2008 #4
    Yeah, thanks for that. But I thought about what mathman said and the answer was obvious, lol. Thanks a lot though for working it out.

    Yeah, so the 2(1/cosx) becomes 2secx...

    That was pretty stupid, lol. Thanks though. This is a little off-topic for this thread but I really lack in courses like physics and math and I really like this forum (I'm new, lol) and what I like is how you guys don't just give an answer. You either show all the steps like Diffy did or what you did and made me think about it. :)
     
    Last edited: Mar 27, 2008
  6. Mar 27, 2008 #5
    I have another question I can't understand.

    Which expression is equivalent to cos(pi + theta) (I don't know how to import the signs. and I checked the computer's character map)

    So what I did was take cos(pi + theta) and put down the formula:

    cos pi * cos theta - sin pi * sin theta

    But I don't know what to do from there. I tried to see if I could do anything putting sin over cos but they're on opposite sides of the "-".

    Choices are: A. -cos theta B. cos theta C. -sin theta D. sin theta
     
  7. Mar 27, 2008 #6
    you have cos(pi) and Sin(pi) in your expressions... What is the cos(pi)? sin(pi)?
     
  8. Mar 27, 2008 #7
  9. Mar 27, 2008 #8
    Thanks for telling me about the symbols. That should come in handy :)


    Just realized this isn't the forum for homework questions so I'm going to make a new thread in the correct section.
     
    Last edited: Mar 27, 2008
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