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Chapter 7
Advanced Features
Note that it was not necessary to determine the inverse of [A] to obtain the solution. EES
calculates the inverse matrix internally, as needed to solve these and any other simultaneous
equations. However, the inverse matrix [A]-1 can be determined by setting the matrix product
[A] [A]-1 equal to the identity matrix in the following manner.
The inverse matrix Ainv will appear in columns of the Arrays window.
The two examples above provide a general procedure for determining the product of a matrix
and a vector or the product of two matrices. Using the DUPLICATE command along with
array variables in EES is no more efficient than the alternative of entering each equation
separately with non-array variable names; however, the matrix capabilities in EES can
significantly reduce the amount of typing required to enter the problem and, more importantly,
make the equations easier to follow.
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