## liliy 2 years ago DOES ANYONE KNOW MATHEMATICA?????

1. modphysnoob

YES

2. modphysnoob

3. liliy

okay: i need to use derivative to verify that : p(x,t) = (1/(Sqrt[4 Pi t])) Exp[ -x^2/(4 t) is the solution of the diffusion equation dp/dt= d^2p/dx^2

4. liliy

i got the value for dp/dt with the function :pt = D[(1./(Sqrt[4 Pi t])) Exp[ -x^2/(4 t)], t]

5. liliy

but my second derivative of dx gives me 0.

6. liliy

dx = D[(1./(Sqrt[4 Pi t])) Exp[ -x^2/(4 t)], {x, 2}] is there soemthign wrong with my equation?

7. liliy

:(

8. modphysnoob

so are you trying to solve differential equation or take second derivative?

9. modphysnoob

second derviative goes like this D[ Type function here ,{x,2}]

10. liliy

ya thats what i did

11. modphysnoob

D[(1./(Sqrt[4 Pi t])) * Exp[ -x^2/(4 t)], {x, 2}]

12. modphysnoob

./ is not used in mathematica, it is matlab notation

13. liliy

./ i was just trying to make the whole thing into a number so i tried to multiple (dividde) by 1. lol

14. liliy