给出了一类上三角形矩阵可交换的充要条件，并由此得到了求其逆矩阵的一种简便方法。
The exchangeable necessary and sufficient condition is given for a class upper triangular matrixes, and out of it, we have got a simple method of obtaining inverse matrixes.
本文给出了上(下)三角形矩阵的一个求逆公式。
This article gives a Formula for finding inverse matrices of upper (down) triangular matrix.
本文在已有的索单元力密度矩阵的基础上推导了三角形膜单元的力密度矩阵。
On the basis of force density matrix of cable element, a force density matrix of triangle membrane element is introduced.
本文在已有的索单元力密度矩阵的基础上推导了三角形膜单元的力密度矩阵。
On the basis of force density matrix of cable element, a force density matrix of triangle membrane element is introduced.
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