Results 1 to 3 of 3

Math Help - question on arcsec infinity

  1. #1
    Newbie
    Joined
    Oct 2009
    Posts
    21

    question on arcsec infinity

    can someone explain to me how arcsec infinity is equal to pi/2? thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Quote Originally Posted by FailCalculus View Post
    can someone explain to me how arcsec infinity is equal to pi/2? thanks
    \sec \theta=\frac{1}{\cos \theta}

    Set the denominator to be 0
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,405
    Thanks
    1328
    Quote Originally Posted by FailCalculus View Post
    can someone explain to me how arcsec infinity is equal to pi/2? thanks
    Strictly speaking, " arcsec(\infty)" isn't \pi/2 or any other number. " \infty" isn't a number so secant is not defined for it. You could, of course, extend the real number system to include "infinities" but there are several different ways to do that- you would have to specify which you meant.

    But, we can talk about this in the limit sense. sec(\theta)= \frac{1}{cos(\theta)} and as \theta goes to \pi/2, cos(\theta) goes to 0 and so sec(\theta)= \frac{1}{cos(\theta) "goes to infinity" (get larger without bound). Thus, if we extend the real numbers sytem in that way, we have that " sec(\pi/2)= \infty" and so " arcsec(\infty)= \pi/2".
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: April 23rd 2011, 12:05 PM
  2. derivative of arcsec
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 18th 2009, 05:14 AM
  3. arcsec proplem pls
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: September 24th 2009, 04:40 PM
  4. Integration by parts of arcsec(x)
    Posted in the Calculus Forum
    Replies: 6
    Last Post: September 8th 2008, 08:25 PM
  5. Replies: 1
    Last Post: February 25th 2008, 04:35 PM

Search Tags


/mathhelpforum @mathhelpforum