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Exercise 3

Avg difficulty 2.5

Suppose that w1=[110−1],w2=[1011]\wvec_1=\fourvec110{-1}, \hspace{24pt} \wvec_2=\fourvec1011 form an orthogonal basis for a subspace WW of R4\real^4.

  1. Find b^\bhat, the orthogonal projection of b=[2−1−67]\bvec=\fourvec{2}{-1}{-6}{7} onto WW.

  2. Find the vector b⊥\bvec^\perp in W⊥W^\perp such that b=b^+b⊥\bvec = \bhat + \bvec^\perp.

  3. Find a basis for W⊥W^\perp. and express b⊥\bvec^\perp as a linear combination of the basis vectors.

Austin, Understanding Linear Algebra, §6.3 Orthogonal bases and projections, Exercise 3

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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.