Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Limit of multi variable func.

  1. Oct 28, 2011 #1
    1. The problem statement, all variables and given/known data

    (x,y)-->(0,0) y*ln (y2+x2)

    2. Relevant equations


    3. The attempt at a solution
    i've tried polar coordinates i end up with sinθ in it don't know how to proceed

    and i've taken several paths like y=0 , x=0 , x=y2 , x=y , x=y3
    they all yeild zero

    Edit : is it right if i after making polar sub. to say that :

    r*sinθ * ln r2 [itex]\leq[/itex] r*ln r2
    because if its right then problem solved :P
    Last edited: Oct 28, 2011
  2. jcsd
  3. Oct 28, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Almost. You need absolute values:

    |r*sinθ * ln r2| [itex]\leq[/itex] r*|ln (r2)|
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook