Results 1 to 3 of 3

Math Help - Limit w/trig functions

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    21

    Limit w/trig functions

    I can do everything that we have covered in class so far except for problems involving trig functions! The ones that bother me the most are when I'm supposed to find the limit when I have something like f(x)=csc(x) and x is approaching pi/2 from the right... Does anyone know of an online tutorial that could help me out with trig functions when finding limits?

    I'm doing the chapter review right now for a test tomorrow, and I am currently stumped with this problem:

    lim x-->0 tan(2x)/tan(pi*x)

    I thought that because I plugged in x and therefore got tan(0)/tan(0), that the limit would be 1. Apparently it is 2/pi. How did that work out?!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Banned
    Joined
    Oct 2008
    Posts
    71
    Quote Originally Posted by tom ato View Post
    I can do everything that we have covered in class so far except for problems involving trig functions! The ones that bother me the most are when I'm supposed to find the limit when I have something like f(x)=csc(x) and x is approaching pi/2 from the right... Does anyone know of an online tutorial that could help me out with trig functions when finding limits?

    I'm doing the chapter review right now for a test tomorrow, and I am currently stumped with this problem:

    lim x-->0 tan(2x)/tan(pi*x)

    I thought that because I plugged in x and therefore got tan(0)/tan(0), that the limit would be 1. Apparently it is 2/pi. How did that work out?!

    tan(2x)/tan(pi*x)= [sin(2x).cos(pi*x)]/[cos(2x).sin(pi*x)]....................1


    But sin(2x)= 2x.\frac{\ sin(2x)}{ 2x}.................................................. ......................................2

    Also sin(pi*x)=  \pi x.\frac{\ sin(\pi x)}{\pi x}.................................................. .......................................3

    Substitute now (2) and (3) into (1) and now let x go to zero we get:


    .................................................2/pi................................................

    Because:



    \lim_{ A to 0}{\frac{\ sin(A)}{ A}} =1.

    And cos(0)=1
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Banned
    Joined
    Oct 2008
    Posts
    71
    I am sorry i forgot to write that tan(0)/tan(0) = 0/0 ,which is undefined ,and not equal to 1
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: September 24th 2009, 09:43 PM
  2. Limit of a trig functions
    Posted in the Calculus Forum
    Replies: 3
    Last Post: January 19th 2009, 09:42 PM
  3. Inverse Trig Functions and Advance Trig
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 24th 2008, 03:13 PM
  4. Trig Equations with Multiple Trig Functions cont.
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 7th 2008, 05:50 PM
  5. Trig Equations with Multiple Trig Functions
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: April 6th 2008, 03:48 PM

Search Tags


/mathhelpforum @mathhelpforum