1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Science Advisor

    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook