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    find the limit as x->pi/2 of:

    (cosh x -1)/(x tanx)


    that tanx is giving me grief. using its power series (expanded about pi/2) doesnt help, as its derivatives etc are undefined. the same goes for trying l'hopital's rule. i thought about using power series expanded about pi/4, but that might give inaccurate results (pi/4 ~= 0.78, which is a lot bigger than 0.1 or the general accuracy concensus).
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    (Original post by elpaw)
    find the limit as x->pi/2 of:

    (cosh x -1)/(x tanx)


    that tanx is giving me grief. using its power series (expanded about pi/2) doesnt help, as its derivatives etc are undefined. the same goes for trying l'hopital's rule. i thought about using power series expanded about pi/4, but that might give inaccurate results (pi/4 ~= 0.78, which is a lot bigger than 0.1 or the general accuracy concensus).

    At a guess => 1/tanx => 0 ??? Just because the tanx term will dominate all the others?
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    (Original post by Lagz)
    At a guess => 1/tanx => 0 ??? Just because the tanx term will dominate all the others?
    Yes.

    (cosh(x) - 1) / x is bounded as x -> pi/2.

    1 / tan(x) -> 0 as x -> pi/2.

    So the product of these two things -> 0 as x -> pi/2.
 
 
 

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