Linear Algebra and Its Applications · Problem 3.2.20

Orthogonality — Gilbert Strang

Mathematics · cosines-projections-onto-lines

Problem

Construct the projection matrices

P_1

and

P_2

onto the lines through the

a

's in Problem 18. Is it true that

(P_1+P_2)^2 = P_1+P_2

? This would be true if

P_1P_2 = 0