@hirnyk 

Yes it is simple

Thank you

with(VectorCalculus):

int( x*y, [x,y] = Triangle( <0,0>, <1,0>, <0,1> ) );

This command give a value.

I want to do a calculation symbolically like this:

with(VectorCalculus):

int( x*y, [x,y] = Triangle( <x1,y1>, <x2,y2>, <x3,y3> ) );

Is it possible ?

I know that

int( x, [x,y] = Triangle( <x1,y1>, <x2,y2>, <x3,y3> ) ); is equal to xg*Se where xg=(1/3)(x1+x2+x3) and Se the area of the triangle

Thanks

with(VectorCalculus):

int( x*y, [x,y] = Triangle( <0,0>, <1,0>, <0,1> ) );

This command give a value.

I want to do a calculation symbolically like this:

with(VectorCalculus):

int( x*y, [x,y] = Triangle( <x1,y1>, <x2,y2>, <x3,y3> ) );

Is it possible ?

I know that

int( x, [x,y] = Triangle( <x1,y1>, <x2,y2>, <x3,y3> ) ); is equal to xg*Se where xg=(1/3)(x1+x2+x3) and Se the area of the triangle

Thanks

Yes you are right and more simple to simplify the functions and piecewise functions. But, I use those functions for other thinks and I think I'm not wrong in my functions. Why the error ?

In my worksheet which I posted, I have only three lines but in your answer we have more and we must use command like add, subs, value, eval.

Thanks again

Yes you are right and more simple to simplify the functions and piecewise functions. But, I use those functions for other thinks and I think I'm not wrong in my functions. Why the error ?

In my worksheet which I posted, I have only three lines but in your answer we have more and we must use command like add, subs, value, eval.

Thanks again

When I execut your command below in Maple 14

S2:=fsolve({x=0,y=0,z=0,w=0},{a=1.0,b=1.0,c=1.0,d=1.0},{a=0..7,b=0..7,c=0..7,d=0..7},avoid=S1);

fsolve don't give a result

When I change the range for a=0..8, I have this result

S1:=fsolve({x=0,y=0,z=0,w=0},{a=1.0,b=1.0,c=1.0,d=1.0},{a=0..8,b=0..7,c=0..7,d=0..7},avoid={a = 2.663589361, b = .2708302726, c = 4.120270119, d = .4866603365});

S1 := {a = 3.619595946, b = 1.405424580, c = 6.769845644, d = 4.120270119}

When I execut your command below in Maple 14

S2:=fsolve({x=0,y=0,z=0,w=0},{a=1.0,b=1.0,c=1.0,d=1.0},{a=0..7,b=0..7,c=0..7,d=0..7},avoid=S1);

fsolve don't give a result

When I change the range for a=0..8, I have this result

S1:=fsolve({x=0,y=0,z=0,w=0},{a=1.0,b=1.0,c=1.0,d=1.0},{a=0..8,b=0..7,c=0..7,d=0..7},avoid={a = 2.663589361, b = .2708302726, c = 4.120270119, d = .4866603365});

S1 := {a = 3.619595946, b = 1.405424580, c = 6.769845644, d = 4.120270119}

@roman_pearce 

Thank you verry much for all your answer

I think calculation take less time and memory if I do not generat a Matrix

I try this

@roman_pearce 

Thank you verry much for all your answer

I think calculation take less time and memory if I do not generat a Matrix

I try this

@hirnyk 

I will send you by email my worksheet to give me your opinion

Perhaps there are ways to do the calculation with less time and memory

@hirnyk 

I will send you by email my worksheet to give me your opinion

Perhaps there are ways to do the calculation with less time and memory

@roman_pearce 

Yes, the Matrix is correct but the construction of large system with GeneratMatrix and solve it with LinearSolve take too large memory and time.

With a matrix of 1500 by 1500, the memory is about 1,5 G bytes with a PC of 2G of memory I can not continu my calculations and Maple don't stop for all a day.

I think using connection with Matlab ?

Best regards

@roman_pearce 

Yes, the Matrix is correct but the construction of large system with GeneratMatrix and solve it with LinearSolve take too large memory and time.

With a matrix of 1500 by 1500, the memory is about 1,5 G bytes with a PC of 2G of memory I can not continu my calculations and Maple don't stop for all a day.

I think using connection with Matlab ?

Best regards

Thank you for the answer, but the problem is not the variable of the derivative:

restart:assume(n,integer):h := piecewise(n::odd, r*n^2, r^2*n^3);

diff(h,r);   # don't work Why ?

restart:h1 := piecewise(And(n::integer, n::odd), r*n^2, r^2*n^3);

diff(h1,r); # work

Why diff does'nt work with assume and work when the condition is given inside piecewise ?

Thank you for the answer, but the problem is not the variable of the derivative:

restart:assume(n,integer):h := piecewise(n::odd, r*n^2, r^2*n^3);

diff(h,r);   # don't work Why ?

restart:h1 := piecewise(And(n::integer, n::odd), r*n^2, r^2*n^3);

diff(h1,r); # work

Why diff does'nt work with assume and work when the condition is given inside piecewise ?