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WI08Ma1bPrachelpset7

# WI08Ma1bPrachelpset7 - x^2 x 1 = 0.0 then you get 1.61803...

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Math 1b Practical February 26, 2009 Help with Mathematica for Problem Set 7 Remember that Mathematica works with matrices as a "list" of rows, each row being a "list". So the matrix A = 1 2 3 4 is entered and diplayed as {{1,2},{3,4}}. Use a dot (period) for matrix product, e.g. A.B . Transpose[A] returns the transpose of A . Inverse[A] returns the inverse of A . Eigenvalues[A] returns the list of eigenvalues. Eigenvalues [1.0 A] returns the eigenvalues in decimal form. Eigenvectors[A] returns the list of corresponding eigenvectors. CAUTION: These are the right eigenvectors, or column-eigenvectors. But they seem to be displayed as rows by Mathematica. If you want the matrix whose COLUMNS are the eigenvectors, you want Transpose[Eigenvectors[A]]. MatrixPower[A, n] returns the n-th power of A . IMPORTANT: Mathematica works symbolically unless you tell it otherwise. E.g. it will give the roots of x^2 - x - 1 = 0 as (1 +- Sqrt[5])/2 . If you want MMA to work in floating point, one way to do this is to introduce a decimal point anywhere. If you ask for the roots of

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Unformatted text preview: x^2 - x - 1 = 0.0 , then you get 1.61803 and -0.618034 . In[1]:= A = 88 1, 2 < , 8 3, 4 << Out[1]= 88 1, 2 < , 8 3, 4 << In[2]:= B = 88 1, − 1 < , 8 3, 2 << Out[2]= 88 1, − 1 < , 8 3, 2 << In[3]:= A.B Out[3]= 88 7, 3 < , 8 15, 5 << In[4]:= Inverse @ A D Out[4]= :8 − 2, 1 < , : 3 2 , − 1 2 >> In[5]:= Transpose @ A D Out[5]= 88 1, 3 < , 8 2, 4 << In[6]:= Eigenvalues @ 1.0 A D Out[6]= 8 5.37228, − 0.372281 < In[7]:= Eigenvectors @ A D Out[7]= :: − 4 3 + 1 6 J 5 + 33 N , 1 > , : − 4 3 + 1 6 J 5 − 33 N , 1 >> In[8]:= Eigenvectors @ 1.0 A D Out[8]= 88 − 0.415974, − 0.909377 < , 8 − 0.824565, 0.565767 << In[23]:= U = Transpose @ Eigenvectors @ 1.0 A D D Out[23]= 88 − 0.415974, − 0.824565 < , 8 − 0.909377, 0.565767 << In[24]:= A.U Out[24]= 88 − 2.23473, 0.30697 < , 8 − 4.88543, − 0.210625 << In[25]:= Inverse @ U D .A.U Out[25]= 98 5.37228, 0. < , 9 − 6.10623 × 10 − 16 , − 0.372281 == In[17]:= MatrixPower @ A, 10 D Out[17]= 88 4783 807, 6972 050 < , 8 10458 075, 15 241 882 <<...
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