## ikram002p one year ago give an example for continues function but not differentiable

1. hartnn

y= |x| it has "V" like shape, at x = 0 it is continuous , but not differentiable.

2. ikram002p

exactly...but how cud i find a function f(x,y) cont but not diff :)

3. amistre64

differentiable has to do with limits, if the limits is not the same from all directions, the limit is undefined.

4. amistre64

edit*** and the derivative of y=|x| is y' = x/|x|

5. ikram002p

in fact not necessary i mean if the limit exist its continues any way .. i wanna continues fun but not diff in f(x,y)

6. hartnn

means a 2 variable function example....hmm

7. ikram002p

yess

8. amistre64

i recall one function i was limiting, but it was an implicit i think

9. amistre64

anything with a undefineable partial should suffice

10. hartnn

yeah, not sure about this, but try f(x,y) = |xy|

11. ikram002p

ok ill try

12. amistre64

f = |x+y|-1 :)

13. amistre64
14. amistre64

|xy| reminds me of one of those paper folded beaks ....

15. ikram002p

it sounds good but i have to check my txt book to use the definition to know if its not diff

16. amistre64

im assuming "not differentiable" means that for some x in R, the derivative does not exist.

17. amistre64

Derelict function comes to mind for some reason as well

18. ikram002p

yes its correct :) but the one u gave is also not continues there is a thm if the fun is diff then its continues ima give a counter example for the oposite situation like give an example for fun is cont but not diff

19. ikram002p

@hartnn gave a good example but one variable im gonna to check if xy is true

20. amistre64

http://www.wolframalpha.com/input/?i=%7Csin%28x%2By%29%7C this one is rather nice looking to me

21. sdfasfasdfasdfasdfafd

im sorry for barging on your question ikram

22. ikram002p

it works !! both |xy| |sin(x+y)| thx both @hartnn @amistre64

23. amistre64

good luck ;)

24. hartnn

cool :) welcome ^_^