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Let S(t)be the number of daylight hours on the tth day of the year 2012 in Rome, Italy. We are given the following data for S(t):

We wish to fit a trigonometric function of the form

f(t)=a+bsin(2蟿蟿366t)+ccos(2蟿蟿366t)

To these data. Find the best approximation of this form, using least squares. How many daylight hours does your model predict for the longest day of the year 2012? (The actual value is 15 hours, 13 minutes, 39 seconds.)

Short Answer

Expert verified

x*r=12.26100.4310-2.8993and the required hours aref*17315.1913 hrs.

Step by step solution

01

The required hours.

From the given data we get the terms below

a+bsin232366+c232366........1a+bsin277366+c277366........2a+bsin2121366+c2121366........3a+bsin2152366+c2152366........4

Therefore, consider the system,

1sin64366cos1543661sin154366cos643661sin242366cos2423661sin304366cos304366abcxA=10121415


If ker(A)=0then, xr*=ATA-1ATbr*.

Since, the kernel of the matrix A is {0}.

So, it is written as,

ATA=4.00002.8732-0.24752.87322.2341-0.17733183ATA-1=3.2823-4.2183-0.0365-4.21835.8725-0.00160.0365-0.00160.5712ATA-1AT=1.1109-0.7970-0.42421.1104-1.15341.47280.9718-1.23720.52290.1757-0.2420-0.4566ATA-1ATbr*=12.26100.4310-2.8993

Thus, it is written as,

role="math" localid="1659702486449" xr*=12.26100.4310-2.8993

And the trigonometry function that best fits the data points is

f*t=12.610+0.4310sin2366t-2.89993cos2366t

Hence,xr*=12.26100.4310-2.8993 and the required hours will bef*(173)15.1913 hrs.

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Most popular questions from this chapter

Consider an n x m matrix A with rank (A) = m. Is it always possible to write A as A = QL where Q is an n x m matrix with orthonormal columns and L is a lower triangular m x m matrix with positive diagonal entries? Explain.

Consider the linear systemAx=b , where

A=[1326]and b=[1020].

a. Draw a sketch showing the following subsets of 2:

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  • The image of AT
  • The solution setSof the system Ax=b

b.What relationship do you observe between(kerA) and im(AT)? Explain.

c. What relationship do you observe betweenrole="math" localid="1660916844921" ker(A) and S? Explain.

d. Find the unique vectorx0 in the intersection ofS and(kerA) . Show x0on your sketch.

e. What can you say about the length of x0compared with the length of all other vectors in S?

To make a trend analysis of six evenly spaced data points, one can use orthogonal polynomials with respect to evaluation at the points \(t = - 5, - 3, - 1,\,\,1,\,\,3,{\rm{ and }}5\).

  1. Show that the first three orthogonal polynomials are

\({p_0}\left( t \right) = 1,\,\,\,\,\,\,{p_1}\left( t \right) = t,{\rm{ and }}{p_2}\left( t \right) = \frac{3}{8}{t^2} - \frac{{35}}{8}\)

(The polynomial \({p_2}\) has been scaled so that its values at the evaluation points are small integers.)

  1. Fit a quadratic trend function to the data \(\left( { - 5,1} \right),\left( { - 3,1} \right),\left( { - 1,4} \right),\left( {1,4} \right),\left( {3,6} \right),\left( {5,8} \right)\).

Let Abe annmmatrix. Is the formula(kerA)=im(AT)necessarily true? Explain.

By using paper and pencil, find the least squaresx* of the system Ax=b, whereA=[111011] andb=[333]. Verify that the vectorb-Ax* is perpendicular to the image of A.

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