Linear Algebra and Its Applications · Problem 3.2.25

Orthogonality — Gilbert Strang

Mathematics · cosines-projections-onto-lines

Problem

In Problem 24, the projection of

b

onto the plane of

a_1

and

a_2

will equal

b

. Find

P = A(A^TA)^{-1}A^T

for

A = [a_1\ a_2] = \begin{bmatrix}1 & 1\\0 & 2\end{bmatrix}