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Exercise 4

Avg difficulty 2.5

Consider the vectors w1=[1100],w2=[0011],b=[2−413].\wvec_1=\fourvec1100,\hspace{24pt} \wvec_2=\fourvec0011,\hspace{24pt} \bvec=\fourvec2{-4}13.

  1. If LL is the line defined by the vector w1\wvec_1, find the vector in LL closest to b\bvec. Call this vector b^1\bhat_1.

  2. If WW is the subspace spanned by w1\wvec_1 and w2\wvec_2, find the vector in WW closest to b\bvec. Call this vector b^2\bhat_2.

  3. Determine whether b^1\bhat_1 or b^2\bhat_2 is closer to b\bvec and explain why.

Austin, Understanding Linear Algebra, §6.3 Orthogonal bases and projections, Exercise 4

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Adapted from Understanding Linear Algebra © 2023 David Austin. Licensed under CC BY 4.0. Source: Understanding Linear Algebra. Imported at revision 3e6dced.