## 20 Reputation

8 years, 286 days

## find and solutions of determining equat...

Hello i want to sort according to u derivatives (k) system.  And finding determining equations system and solving this system. Thank you very much.

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## over detemined system...

i have got alot of mixed and high degree derivatives. For example:

u[x]*u[x,t]*eta[x,t]+u[]^2*u[x]*eta[x]+kis(x,y)u[x,t]^2*u[]+eta(x, y)*u[]*u[x]^2+ksi[x,t]*u[x]^2*u[x,t]+......

like this alot of terms

my question is how can i solve divided by the derivative of the u(x,t) partial differential equations system and so  how can i find eta(x,t,u) and ksi(x,t,u)

## how can i sort data like below ...

How can i sort like below? i want to sort x dependent y is fixed

Original case          sorted case

x   y                         x(i)   y[]

2   1                         1      4

3   2                         2      1

5   3                         3      2

1   4                         4      5

4   5                         5      3

## How can I draw following piecewise close...

Maple

How can I draw following piecewise closed function t in  3-dimensional cartesian space

D124:=max(-x+y+z,x-y+z,x+y-z)=1;
D134:=max(-x+y+z,x-y+z,-x-y-z)=1;
D123:=max(-x+y+z,x+y-z,-x-y-z)=1;
D234:=max(x+y-z,x-y+z,-x-y-z)=1;

t:=piecewise(x>0 and y>0 and z>0,D124,x<0 and y<0 and z>0,D134,x<0 and y>0 and z<0,D123,x>0 and y<0 and z<0,D234);

## Closed piecewise function in 3-dimension...

Maple

How can I draw following piecewise closed function in  3-dimensional cartesian space

t:=piecewise(x>0 and y>0 and z>0,D124,x<0 and y<0 and z>0,D134,x<0 and y>0 and z<0,D123,x>0 and y<0 and z<0,D234);

max(-x + y + z, x - y + z, x + y - z) = 1 ,  0 < x and 0 < y and 0 < z
max(-x - y - z, -x + y + z, x - y + z...

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