Author 
Comment/Response 
Rick Hladik

09/23/00 10:57am
{s} is a 2 component vector. s(1)=Sin(Pi x), s(2)=Sin(2 Pi x). [B] is a 2 x 2 matrix. [B] is defined as B(1,1)=Integral[(0,1),s(1)*s(1)], B(1,2)=Integral[(0,1),s(1)*s(2)],
B(2,1)=Integral[(0,1),s(2)*s(1)], B(2,2)=Integral[s(2)*s(2)]. (Please note, I am new to Mathematica and the above equations are not necessarily the way they must be entered, they are only trying to convey the operations without the mathematical symbols)
For some reason when I define the matrix [B] in this type of fashion and then try to invert it, I recieve the message that [B] is not a square matrix....However, this is not the case....Furthermore, If I actually solve each matrix component as a real number rather than leaving it in the formula form, I can then invert without a problem....The only difference in the output cells of the two forms of the matrix before I attempt to invert them is that the formula version appears as {{{.5 Pi^2},{0}},{{0},{2 Pi^2}}} and the real number version output cell appears as {{.5 Pi^2,0},{0,2 Pi^2}}....Note, the number of brackets seems to be the only difference! Yet one inverts and the other will not.
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