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Question: multiple integal

Question:multiple integal

casperyc 962 Maple
May 01 2008
0

hi

i am doing a multiple integal integration from one of my tutorial sheet

 

Given D is the triangular region whose vertices are (0, 0), (Pi,0), (Pi,Pi), find

Int(Int(x*cos(x+y),x),y);

 

then I worked out something like

 

Int(Int(x*cos(x+y),y=0..x),x=0..Pi);value(%);                                         

 

#eqn#

 

the answer gives me a NEGATIVE value..

 

if i do it but hand i get something at last

Int(-x*sin(2*x)+x*sin(x),x=0..Pi);value(%);

 

-3/2*Pi

 

which is as expected

 

 

what;s wrong with my equation ?? #eqn#
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