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!

Limits with trigs

  1. May 28, 2014 #1
    I am having trouble solving limits with trig functions.

    limx→0 x+xcosx/sinxcosx

    useful equation limθ→0 sinθ/θ = 1

    my attempt

    x+xcosx/sinxcosx

    x/sinxcosx + xcosx/sinxcosx

    x/sinx*1/cosx + x/sinx this is where I am getting stuck
     
  2. jcsd
  3. May 28, 2014 #2

    jedishrfu

    Staff: Mentor

    the answer is right in front of you.

    As x approaches zero then what is the value of cosx?

    and you have the sinx/x as x approaches zero so everything is there for you
     
  4. May 28, 2014 #3

    Does x/sinx = 1 also?

    I thought sinx had to be in the numerator for it to = 1
     
  5. May 28, 2014 #4
    Technically, you're right. But note that if ##x\neq 0##, then ##\frac{x}{\sin x}=\frac{1}{\frac{\sin x}{x}}##, and you have something to which you can apply your limit law for ratios.

    So I guess technically you're not right (with regard to the value of the limit), but it's good to be skeptical. I had some students a year or so ago that got marked down (per a grading rubric that was not mine) for omitting the step that I showed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Limits with trigs
  1. Trig Limit (Replies: 1)

  2. Trig Limits (Replies: 2)

  3. Trig Limit (Replies: 4)

  4. Trig limit. (Replies: 5)

  5. Trig Limits (Replies: 9)

Loading...