matlab小题不会

来源：百度知道 编辑：UC知道 时间：2024/05/31 02:49:50
A=[1,0.84555919 ,0.755978422,0.699613473,0.603236631,0.436647836,0.292528565,0.238584717,0.137747951,0.060654972;
0.84555919,1,0.84555919 ,0.755978422,0.699613473,0.603236631,0.436647836,0.292528565,0.238584717,0.137747951;
0.755978422,0.84555919,1,0.84555919 ,0.755978422,0.699613473,0.603236631,0.436647836,0.292528565,0.238584717;
0.699613473,0.755978422,0.84555919,1,0.84555919 ,0.755978422,0.699613473,0.603236631,0.436647836,0.292528565;
0.603236631,0.699613473,0.755978422,0.84555919,1,0.84555919 ,0.755978422,0.699613473,0.603236631,0.436647836;
0.436647836,0.603236631,0.699613473,0.755978422,0.84555919,1,0.84555919 ,0.755978422,0.699613473,0.603236631;
0.292528565,0.436647836,0.603236631,0.699613473,0.755978422,0.84555919,1,0.84555919 ,0.755978422,0.699613473;
0.238584717,0.292528565,0.436647836,0.603236631,0.699613473,0.755978422,0.84555919,1,0.84555919 ,0.755978422;
0.137747951,0.238584717,0.292528565,0.436647836,0.603236631,0.699613473,0.75

inv(A)*b

ans =

1.0000
-0.0000
-0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0

A直接乘以b
A:n*n
b:n*1
点乘得满足两数组尺度一样b:n*n

题目故意的吧

这个结果是正确的，因为，你题目里面的b正好是A的第一列，因此
inv(A)*A= [inv(A)*A(:,1), inv(A)*A(:,2),.....inv(A)*A(:,size(A,2)]
因为inv(A)*A = I =
[1 0 ....0
0 0 ....0
. . ....0
. . ....0
0 0 ....0];因此，inv(A)*A(:,1)=[1,0,...0]';
而又因为b=A(:,1)
即有inv(A)*b=[1,0...0]'
因此从理论和实践上来讲，结果都是对的。
test1=inv(A)*A(:,1)

test1 =

1.0000
-0.0000
-0.0000
0.0000
-0.0000
-0.0000
-0.0000
0.0000
-0.0000
-0.0000

>> test2=inv(A)*b

test2 =

1.0000
-0.0000
-0.0000
0.0000
-0.0000
-0.0000
-0.0000
0.0000
-0.0000