Let C be a symmetric matrix of rank one.Prove that C must ha

Given two sets A,B,the symmetric difference of A and B is denoted by
A△B and defined as A△B = (A − B) ∪ (B − A).
For very sets A,B,C,prove that:
A△(B△C) = (A△B)△C
翻译：对于集合A、B,有：A△B = (A − B) ∪ (B − A).证明：A△(B△C) = (A△B)△C

翻译一段英文算法
1. Build the symmetric non-negative n x n matrix M as
described in Section 2.
2. Let x3 be the principal eigenvector ofM. Initialize the
solution vector x with the n x 1 zero vector. Initialize
L with the set of all candidate assignments.
3. Find a3 = argmaxa2L(x3(a)). If x3(a3) = 0 stop
and return the solution x. Otherwise set x(a3) = 1
and remove a3 from L.
4. Remove from L all potential assignments in conflict
with a3 = (i, i0). These are assignments of the form
(i, k) and (q, i0) for one-to-one correspondence constraints
(they will be of the form (i, k) for one-to-many
constraints).
5. If L is empty return the solution x. Otherwise go back
to step 3.

英语翻译
where b 2 rmþn; k 2 rm2m is symmetric positive definite,
b 2 rm2n has full column rank,and c 2 rn2n is
symmetric positive semi-definite.a more detailed
description of biot1s consolidation equations is given
elsewhere [1].it suffices to note here that the number
of displacement degrees of *** (dofs) m and the
number of pore pressure dofs n has a ratio of about
0.1 (see table 1 for examples).the matrix a is generally
sparse.fig.1 illustrates the sparsity pattern of a from
a 5· 5 · 5 meshed footing problem.a wide class ofconstrained problems involving mixed finite-element
formulations also produces the above 2 · 2 block matrix
structure [2].

英语翻译
This ensures a symmetric expansion of the resistors and a maximum stability to high load impulses.The aluminium profile with the fixed resistor element is filled with quarts sand石英砂.This ensures a minimum change of the resistor surface temperature even if the resistor element reaches its maximum temperature during a pulse load.If higher protection classes are required please use our CCR,CBR or CBT resistors.The highest protection class is IP65 / Type 4X,and the power range is up to 6 kW

请帮忙翻译,毛衫的,要专用术语
the neck hole should been symmetric and shape Rib edges must not tear>runs are not accepted Sleeves must be of equal length
Don't press too much
there are some color yarn in the sample>it don't happen when produce.
the beads should be fixed
Avoid thick yarns,holes and runs
Be carefull with packing>don't pull threads
Measurements:
must samed as measurements chart

线性代数证明题
A square matrix is called skew-symmetric if AT = ..A.Prove that if A
is an (2k +1)(2k +1) skew-symmetric,k = N(natural number),then A is a nonsingular
matrix.