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Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) §11.4 Matrices and Linear Equations, #43 · Linear Algebra · Linear systems

(c) Does … exist

Multiplying by $P = [.5 .5 .5 .5]$ projects $u$ onto the $4 5^{\circ}$ line.

(a) Find the projection $P u$ of $u = [10]$ .

(b) Why does $P$ times $P$ equal $P$ ?

(c) Does $P^{- 1}$ exist? What vectors give $P u = 0$ ?

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Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) · §11.4 Matrices and Linear Equations, #43

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