Matrix Powers

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Robert Fox

Math SL

12/09/2007


Table of contents: Questions:

  1. Consider  the Matrix M=

Calculate Mn for n= 2, 3, 4, 5, 10, 20, 50. Describe in words any pattern you observe. Use this pattern to find a general expression for the matrix Mn in terms of n.

  1. Consider the matrices P=  and S=

             P2= 2 = =; S2= 2 = =

            Calculate Pn and Sn for other values of n and describe any pattern you observe.

  1.  Now consider matrices of the form  steps 1 and 2 contain examples of these matrices for K=1 2 and 3. Consider other values of k, and describe any pattern(s) you observe. Generalize these results in terms of K and N

  1. Use technology to investigate what happens with further values of k and n. State the scope or limitations of k and n.

  1. Explain why your results holds true in general.

SL type 1: Matrix Powers

1)

  1. To calculate the value for matrix ‘M’ when n=2, the matrix  must be multiplied by an exponent of 2. This would be shown and calculated as,  x

Therefore the value of matrix M2 =

  1. To calculate the value for matrix ‘M’ when n=3, the matrix  must be multiplied by an exponent of 3. Therefore the value of M3 =
  2. To calculate the value for matrix ‘M’ when n= 4, the matrix x  must be multiplied by an exponent of 4. Therefore the value of M4=
  3.  To calculate the value for matrix ‘M’ when n=5, the matrix  must be multiplied by an exponent of 5. Therefore the value of M5=
  4.   To calculate the value for matrix ‘M’ when n=10, the matrix  must be multiplied by an exponent of 10. Therefore the value of M10=
  5.  To calculate the value for matrix ‘M’ when n= 20, the matrix  must be multiplied by an exponent of 20. Therefore the value of M20=
  6. To calculate the value for matrix ‘M’ when n=50, the matrix  must be multiplied by an exponent of 50. Therefore the value of M50=

Looking in more detail at the previous calculations for matrix ‘M’, a clear pattern was observed. It was observed that when the value for ‘n’ increased, an increase of the numbers of the top left and bottom right of the matrix occurred but the two remaining numbers remained “0”. It was shown that the numbers inside the matrix were increasing exponentially with the increase of ‘n’. Therefore a general expression for the matrix Mn in terms of ‘n’ was derived to be:

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This expression supports the pattern observed.

2)

As observed from the previous question, the numbers inside the matrix are getting further apart exponentially. It is noticed that if the matrix is simplified by an exponentially growing scale factor, the elements in the matrix will remain within 2 of each. Therefore for the scale factor to increase by 2 it must exponentially increase by 2 also.

Calculations when n=3:

P3=3== 4 

S3=3==

Calculations when n=4:

P4= 4= = 8

 S4= 4= =8

Calculations when n=5:

P5=5=  = 16

S5=5= ...

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